PROCEEDINGS

OF THE

EOYAL SOCIETY OF LONDON.

From June 2, 1892, to February 9, 1893.

VOL. LII.

LONDON: HARRISON AND SONS, ST. MARTIN'S LANE,

in ©ririnarg to Her iHaj-estg. MDCCCXCITI.

V-5-L

LONDON :

HARRISON AND SONS, PEINTEES IN OEDINARY TO HER MAJESTY, ST. MARTIN'S LANE.

CONTENTS.

VOL. LIL

No. 315.— June 2, 1892.

Election of Fellows 1

On the Method of Examination of Photographic Objectives at the Kew Observatory. By Major L. Dai-win , 2

Supplementary Report on Explorations of Erect Trees containing Animal Remains in the Coal-Formation of Nova Scotia. By Sir J. William Dawson, F.R.S 4

The Hippocampus. By Alex. Hill, M.D., Master of Downing College 5

On a new Form of Air Leyden, with Application to the Measure- ment of small Electrostatic Capacities. By Lord Kelvin, P.RS 6

On certain Ternary Alloys. Part VI. Alloys containing Aluminium, together with Lead (or Bismuth) and Tin (or Silver). By C. R. Alder Wrigjit, D.Sc., F.R.S., Lecturer on Chemistry and Physics in St. Mary's Hospital Medical School 11

The Conditions of the Formation and Decomposition of Nitrous Acid. By V. H. Veley, M.A., University Museum, Oxford 27

On the Theory of Electrodynamics, as affected by the Nature of the Mechanical Stresses in Excited Dielectrics. By J. Larmor, M.A., Fellow of St. John's College, Cambridge 55

On Current Curves. By Major R. L. Hippisley, R.E. [Title only] .... 67

List of Presents 67

June 16, 1892.

On a Multiple Induction Machine for producing High Tension Elec- tricity, and on some remarkable Results obtained with it. By the Lord Armstrong, C.B., F.R.S. [Title only} 70

On certain Appearances of Beams of Light, seen as if emanating from Candle or Lamp Flames. By the late Professor James Thomson, F.R.S 70

Voltaic Cells with Fused Electrolytes. By J. Brown 75

The Physiological Action of the Nitrites of the Paraffin Series con- sidered in connexion with their Chemical Constitution. Part II. Action of the Nitrites on Muscular Tissue and Discussion of Results. By J. Theodore Cash, M.D., F.R.S., Professor of Materia Medica in the University of Aberdeen, and Wyndham R. Dunstan, M.A., Professor of Chemistry to the Pharmaceutical Society of Great Britain 91

On the Estimation of Uric Acid in Urine : a new Process by means of Saturation with Ammonium Chloride. By F. Gowland Hopkins, B.Sc., Gull Research Student at Guy's Hospital 93

IV

Page

On the Potential Difference required to produce a Spark between two Parallel Plates in Air at different Pressures. By J. B. Peace, M.A., Fellow of Emmanuel College, Cambridge ................................................ 99

Electro-chemical Effects on Magnetising Iron. Part IV. By Thomas Andrews, F.R.S., M.Inst.C.E ..................................................................... 114

Note on the Spectra of the Flames of some Metallic Compounds. By G. D. Liveing, M.A., F.E.S., Professor of Chemistry, and J. Dewar, LL.D., F.R.S., Jacksonian Professor, University of Cambridge. [Plate 1] ........................................................................................................ 117

Preliminary Note on the Pressure developed by some New Explosives. By Captain Noble, C.B., F.R.S ................................................................. 123

The Reserve Proteid of the Asparagus Root. By S. H. Vines, F.R.S., and J. R. Green, M.A., F.L.S ................ ..................................................... 130

Note oja the Structure .of Rhdbdopleura. By G. Herbert Fowler, B.A., Ph.D., Assistant in the Zoological Laboratory of University College, London ........... . ................................................................................ 132

On the Flask-shaped Ectoderm and Spongoblasts in one of the Kera- tosa. By George Bidder ............................................................................ 134

Contributions to the Anatomy of Fishes. II. The Air-Bladder and Weberian Ossicles in the Siluroid Fishes. By T. W. Bridge, M.A., Professor of Zoology in the Mason College, Birmingham, and A. C. Haddon, M.A., Professor of Zoology in the Royal College of Science, Dublin ............................... . ........................................................................... 139

On the early Development of Cirripedia. By Theo. T. Groom, B.A., B.Se., F.G.S., Demonstrator in Zoology at the Yorkshire College, Leeds, late Scholar of St. John's College, Cambridge ............................ 158

Thermal Radiation in Absolute Measure. By J. T. Bottom ley, M.A., D.Sc., F.R.S .......... ............................................ .. ........................... „. ........... ; 162

The Cerebrum of Ornithorhynchus paradoxus. By Alex. Hill, M.D ..... 163 Contribution to the History of the Interchange of Pulmonary Gases in the Respiration of Man. By William Marcet, M.D., F.R.S. [Title only} .................................... ... ................................ '. ........... 164

Magnetic Properties of Pure Iron. By Francis Lydall and Alfred W. S. Pocklihgton. [Title only] ................................ .. .............................. 164

On the Alimentary Canal of Pontia brassica*. By A. B. Griffiths. [Title oity] ............................ . ........ , ....... . ................ . ................................................. 165

On a new Method for the Bacteriological Examination of Water, and on a new Bacillus discovered in Rain-water. By A. B. Griffiths. [Title only] ................................................................................................................ 165

List of Presents

No. 316.

On a Multiple Induction Machine for producing High Tension Elec- tricity, and on some remarkable Results obtained with it Bv Lord Armstrong, C.B., F.R.S. [Plates 2—13] \ .. ne

On the Simultaneity of Magnetic Variations at different places on occa- sions of Magnetic Disturbance, and on the Relation between Magnetic and Earth Current Phenomena. By William Ellis, F.R.A.S. Super- intendent of the Magnetical and Meteorological Department Roval Observatory, Greenwich 191

Page

Contribution to the History of the Interchange of Pulmonary Gases in the Eespiration of Man. By William Marcet, M.D., F.R S 213

Magnetic Properties of Pure Iron. By Francis Lydall and Alfred W.

S. Pocklington 228

On the Shoulder Girdle in Ichthyosauria and Sauropterygia. By J. W.

Hulke, F.R.S 1 233

On Current Curves. By Major R. L. Hippisley, R.E 255

No. 317.— November 17, 1892.

On the Characters and Behaviour of the Wandering (Migrating) Cells of the Frog, especially in relation to Micro-organisms. By A. A. Kanthack, M.R.C.P., M.B., and W. B. Hardy, M.A 267

Stability and Instability of Viscous Liquids. By A. B. Basset, M.A., F.R.S 273

On the Colour of the Leaves of Plants and their Autumnal Changes. By Arthur Hill Hassall, M.D. London. [Title only} 276

Observations on the Earthquake Shocks which occurred in the British Isles and France during the month of August, 1892. By Edward Hull, F.R.S., F.G.S., Professor of Geology in the Royal College of Science. [Title only] 276

List of Presents 276

November 24, 1892.

Ionic Velocities. By W. C. Dampier Whetham, B.A., Fellow of Trinity College, Cambridge 283

Memoir on the Theory of the. Compositions of Numbers. By P. A. MacMahon, Major R*.A., F.R.S 290

List of Presents 294

November 30, 1892. ANNIVERSARY MEETING.

Report of Auditors 299

List of Fellows deceased since last Anniversary 299

elected 300

Address of the President , 300

Election of Council and Officers 315

Financial Statement 316 319

Trust Funds 320—324

Table showing Progress and present State of Society with regard to Fellows 325

Account of Grants from the Donation Fund 325

No. 318.— December 8, 1892.

On the Photographic Spectra of some of the Brighter Stars. By J. N. Lockyer, F.R.S 326

On the Velocity of Crookes' Cathode Stream. By Lord Kelvin, P.R.S. . 331

VI

Page

Experiments in Examination of the Peripheral Distribution of the Fibres of the Posterior Roots of some Spinal Nerves. By C. S. Sherrington, M.A., M.D., Lecturer on Physiology at St. Thomas's Hospital, London 333

Preliminary Account of the Nephridia and Body Cavity of the Larva of Palcemonetes varians. By Edgar J. Allen, B.Sa, University College, London 338

List of Presents 343

December 15. 1892.

On an Apparatus for facilitating the Reduction of Tidal Observations. By G. H. Darwin, F.R.S., Plumian Professor and Fellow of Trinity College, Cambridge 345

On some new Reptiles from the Elgin Sandstone. By E. T. Newton, F.G.S 389

The Electromotive Properties of the Skin of the Common Eel. By E. Waymouth Reid, Professor of Physiology in University College, Dundee . 391

Preliminary Note on the Relation of the Ungual Corium to the Peri- osteum of the Ungual Phalanx. By F. A. Dixey, M.A., M.D., Fellow of Wadham College, Oxford 392

Experiments on the Action of Light on Bacillus anthracis. By H. Marshall Ward, F.R.S., Professor of Botany, Royal Indian Engineer- ing College 393

List of Presents 400

On the Method of Examination of Photographic Lenses at the Kew Observatory. By Leonard Darwin, Major, late Royal Engineers .... 403

No. 319.— January 19, 1893.

BAKERIAN LECTURE.— The Rate of Explosion in Gase?. By Harold B. Dixon, M.A., F.R.S., Professor of Chemistry in the Owens College, Manchester 451

List of Presents 453

January 26, 1893.

On the Physiology of the Embryonic Heart (Preliminary Communi- cation). By J. W. Pickering, B.Sc., Assistant Demonstrator in Biology at St. Bartholomew's Medical School 461

Further Researches in Connexion with the Metallurgy of Bismuth. By Edward Matthey, F.S.A., F.C.S., Asscc. Roy. Sch. Mines 467

On the Three-Bar Motion of Watt. By William Brennand 472

List of Presents 474

No. 320.— February 2, 1893.

A New Portable Miner's Safety-lamp, with Hydrogen Attachment for Delicate Gas-testing ; with Exact Measurements of Flame-cap Indi- cations furnished by this and other Testing Lamps. By Frank Clowes, D.Sc. Lond., Professor of Chtmibtry, University College, Nottingham 484

Page

On a Meteoric Stone found at Makariwa, near Invercargill, New Zea- land. By G. H. F. Ulrich, F.G.S. Professor of Mining and Minera- logy in the University of Dunedin, N.Z 504

On Operators in Physical Mathematics. Part I. By Oliver Heaviside, F.R.S 504

On Certain Ternary Alloys. Part VII. Alloys containing Zinc, to- gether with Lead (or Bismuth) and Cadmium (or Antimony). By C. R. Alder Wright, D.Sc., F.R.S., Lecturer on Chemistry and Physics in St. Mary's Hospital Medical School 530

List of Presents 543

February 9, 1893.

Preliminary Account of the Arrangement of the Sympathetic Nervous System, based chiefly on Observations upon Pilo-mo^or Nerves. By J. N. Langley, F.R.S., Fellow of Trinity College, Cambridge. [Plate 14] 547

Note on the Knee- jerk and the Correlation of Action of Antagonistic Muscles. By C. S. Sherrington, M.A., M.D 556

On the Leucocytes of Peptone and other Varieties of Liquid Extra- vascular Blood. By A. E. Wright, M.D., Professor of Pathology, Army Medical School, Netley "... 5(34

List of Presents 569

Obituary Notices :—

Sir William Bowman i

Carl Schorlemmer vii

Henry Tibbats Staiuton ix

Thomas Archer Hirst x{

Edward Killwick Calver xviii

xxi

. PROCEEDINGS

OF

THE ROYAL SOCIETY.

June 2, 1892.

The Annual Meeting for the Election of Fellows was held this day The LORD KELVIN, D.C.L., LL.D., President, in the Chair.

The Statutes relating to the election of Fellows having been read, reneral Clerk and Mr. Crookes were, with the consent of the Society, nominated Scrutators to assist the Secretaries in examining the lists.

The votes of the Fellows present were then collected, and the fol- lowing candidates were declared duly elected into the Society :

Armstrong, Robert Young, Lieut. -

Col. R.E.

Beddard, Frank Evers, M.A. Fleming, Professor John Ambrose,

D.Sc. Foster, Professor Clement Le

Neve, D.Sc.

Gadow, Hans, M.A., Ph.D. Giffen, Robert, LL.D. Gotch, Professor Francis, M.A.,

M.R.C.S.

Herdman, Professor William

Abbott, D.Sc. Hutton, Capt. Frederick Wollas-

ton.

Joly, John, M.A. Larmor, Joseph, D.Sc. Miall, Professor Louis C. Peach, Benjamin Neve, F.R.S.E. Pedler, Professor Alexander,

F.I.C. Waller, Augustus D., M.D.

Thanks were given to the Scrutators.

June 2, 1892. The LORD KELYIN, D.C.L., LL.D., President, in the Chair.

A List of the Presents received was laid on the table, and thanks ordered for them.

The following Papers were read : VOL. LII,

Major L. Darwin. On the Method of [June 2,

I. "On the Method of Examination of Photographic Objectives at the Kew Observatory." By Major L. DARWIN. Com- municated by Captain ABNEY, R.E., F.R.S. Received

April 13, 1892.

(Abstract.)

The paper describes the method of examination of photographic objectives which has been adopted at the Kew Observatory, chiefly on the recommendation of the author. In selecting and devising the different tests, Major Darwin acted in co-operation with Mr. Whipple, the Superintendent of the Observatory, and was aided by consulta- tions with Captain Abney.

The object of the examination is to enable any one, on the pay- ment of a small fee, to obtain an authoritative statement or certificate as to the quality of an objective for ordinary purposes ; the amount of time that can be devoted to each experiment is therefore strictly limited.

An example is first given of a "Certificate of Examination" snch as would be obtained from Kew, and then the different tests are dis- cussed in detail. Many of them are done by well-known methods, which need not here be mentioned. For the greater part of the ex- amination, an apparatus called the " testing camera " is employed, and this is fully described in the paper. The following are the different items in the Certificate of Examination, including the various tests to which the objective is subjected, or the subjects about which in- formation is given :

(1.) to (4.) Under these headings are given a description of the objective, the date of receipt, the size of the plate for which the objective is to be examined, &c., &c. None of this information forms part of the result of the testing.

(5.) Number of Reflecting Surfaces of the Lenses.

(6.) Centering in Mount.

(7.) Visible Defects, such as Veins, Feathers. Sec.

(8.) Flare Spot.

(9.) Effective Aperture of Stops, which is given for each one sup- plied with the objective. In recording the results, it is proposed that the system of numbering recommended by the International Photo- graphic Congress of Paris of 1889 should be adopted.

(10.) Angle of Cone of Illumination, ^c.— Under this heading several useful items of information are given, such as the extreme angle of the field which is illuminated by the objective without •eference to definition; the angle of field which is required to cover the plate of the size for which the objective is being examined ; and the largest stop of which the whole opening can be seen from the

im ca

1892.] Examination of Photographic Objectives at Kew. 3

whole of the plate. With reference to this last item, it is shown how if a larger stop than the one here named is used, the illumination will fall off very rapidly towards the edges of the plate, whereas there will be no improvement in this respect by using a smaller stop.

(11.) Principal Focal Length. This is found by revolving the camera through a known angle, and measuring the movement of the image of a distant object on the ground glass ; with the testing

mera it is so arranged that an angular movement can be given with great ease and accuracy, and that the angle is such that half the focal length is directly read off on a scale on the ground glass. The observation is made, and the focus adjusted, when the image is at a point some 14 degrees from the axis of the objective, and the effect of distortion and curvature of the field is discussed ; it is proved that the focal length thus obtained, even though it may not be identical with the principal focal length as measured on the axis, is never- theless what the photographer in reality wants to ascertain.

(12.) Curvature of the Field. The amount of movement of the ground glass to adjust the focus at different parts of the field is measured, and the results are recorded to show the curvature. A table is given by which it can, be seen what is the largest stop which can be used so as to produce negatives up to a certain standard of excellence in definition.

(13.) Distortion. This test depends in principle on ascertaining the sagitta or deflection in the image of a straight line along one side of the plate. In the discussion it is shown that to give the total dis- tortion near the edge of the plate would not answer practical require- ments, and that the proposed method of examination does give the most useful information that can be supplied.

(14.) Definition. This is found by ascertaining what is the thinnest black line the image of which is just visible when seen against a bright back-ground. It is shown that this is the best method that could be devised of measuring the defining power of an objective, and that it is not open to serious objections on theoretical grounds.

(15.) Achromatism. Under this heading is recorded the difference of focus between an object when seen in white light and the same when seen in blue or red light. How to estimate approximately the diffusion in the image due to any defect in achromatism is discussed.

(16.) Astigmatism. This test is performed by measuring the dis- tance between the focal lines at the corner of the plate, and by cal- culating from the result thus obtained the approximate diameter of the disc of diffusion due to astigmatism. The reflection of a lamp in a thermometer bulb is employed to give a fine point of light, and the positions of the focal lines are obtained by noting when the imnge of the object appears as a fine line, first in one direction, and then in another, as the focus is altered.

B 2

4 Animal Remains in llie Coal of Nova Scotia. [June 2,

(17.) Illumination of the, Field.— The method of examination, which is due to Captain Abney, is described. The question of the falling off cf the intensity oi illumination from the centre of the plate is discussed.

II. " Supplementary Report on Explorations of Erect Trees containing Animal Remains in the Coal-Formation of Nova Scotia." By Sir J. WILLIAM DAWSON, F.R.S. Received April 25, 1892.

To the memoir which I had the honour to present to the Royal Society on this subject in 1882* I appended a note from Dr. Scudder, of Cambridge, U.S., so well known for his researches in fossil Insects and Arachnidans, in which he gave a preliminary account of the remains of Arthropods in my collections which I had submitted to him. He has only in the present year completed his examination of these remains, most of which are very fragmentary, and much damaged by unequal pressure. The result has been embodied in a Report on Canadian Fossil Insects, now in course of publication by the Geological Survey of Canada.

In this report he will describe from the contents of the Sigillarian stumps extracted by me, with the aid of the grant of this Society, three new species of Myriapoda, making, with the five previously known from these remarkable repositories, eight in all, belonging to two families, Archiulidaa and Euphoberida3, and to three genera, Archiulus, Xylobius, and Amynilyspes. The three new species are Archiulus euphoberioides, Sc., A. Lyelli, Sc., and Amynilyspes (sp.). The remains of Scorpions he refers to three species, Mazonia acadica, Sc., Mazonia (sp.), and a third represented only by small fragments. The characters of the species referred to Mazonia he considers as tending to establish the generic distinctness of Mazonia from Eoscor- pius. Dr. Scudder also notices the fragment of an insect's head con- taining part of a facetted eye, mentioned in my memoir, and considers it probably a portion of a Cockroach.

Much credit is due to Dr. Scudder for the care and skill with which he has worked up the mostly small and obscure fragments which I was able to submit to him, and which are probably little more than debris of the food of the Amphibians living for a time in these hollow stumps, and devouring such smaller animals as were so unfortunate as to be imprisoned with them. In this connexion the suggestion of Dr. Scudder is worthy of attention, that the scaly armour of the smaller Microsaurians may have been intended to

fend them against the active and venomous Scorpions which were temporaries, and some of which were sufficiently large to * ' Phil. Trans.,' 1S82, p. 621.

1892.] Dr. A. HiJl. The Hippocampus. 5

be formidable antagonists to the smaller land Vertebrates of the period.

The report of Dr. Scudder will complete the account of the land animals of the erect Sigillariee of the South Joggins, unless by new falls of the cliff fresh trees should be exposed. From 1851, when the first remains were obtained from these singular repositories by the late Sir Charles Lyell and the writer, up to the present time, they have afforded the remains of twelve species of Amphibians, three land Snails, eight Millipedes, three Scorpions, and an Insect.

The type specimens of these animals have been placed in the Peter Redpath Museum of McGill University, and such duplicates as are available will be sent to the British Museum and that of the Geological Survey of Canada.

III. " The Hippocampus." By ALEX HILL, M.D., Master of Downing College. Communicated by Prof. A. MACALISTER, M.D., F.R.S. Received May 4, 1892.

(Abstract.)

The subject of this paper is the hippocampal region of the brain in anosmatic animals. Several specimens of the brain of the bottle- nosed, whale, narwhal, porpoise, and calf-seal were obtained for the purpose of studying the extent to which the hippocampus in animals totally destitute of the sense of smell, or possessing it in a very small degree, departs from the ordinary type.

The hippocampal region was, in each case, cut into a series of

ectiohs, which showed that there is, in the brains of Hyperoodon

and Monodon, no fascia dentata; in Phocoena this formation is very

rudimentary ; in Phoca it is rather less strongly developed than in

man.

As a standard of comparison, the hippocampus of the ox was studied in a similar manner. Certain points which have not been described hitherto with regard to the anatomy and histology of the hippocampus in macrosmatic brains are noticed. Other peculiarities in the general form and in minute structure which distinguish the brains of anosmatic animals are also mentioned incidentally.

The discovery that the fascia dentata is completely absent in animals which possess no olfactory bulb or tract, and that it varies in development directly as the size of these organs, throws light upon the function of the hippocampal region, and seems to call for a fresh definition of its several parts and a revision of the nomenclature of the region. The paper contains an historical survey of the ter- minology and suggestions for its revision.

Lord Kelvin. On a new Form of Air Leyden, [June 2,

IV. " On a new Form of Air Ley den, with Application to the Measurement of Small Electrostatic. Capacities." By LORD KELVIN, P.R.S. Received May 31, 1892.

In the title of this paper as originally offered for communication " Air Condenser " stood in place of "Air Leyden," but it was accom- panied by a request to the Secretaries to help me to a better designa- tion than "Air Condenser" (with its ambiguous suggestion of an apparatus for condensing air), and I was happily answered by Lord Rayleigh with a proposal to use the word " leyden " to denote a generalised Leyden jar, which I have gladly adopted.

The apparatus to be described affords, in conjunction with a suit- able electrometer, a convenient means of quickly measuring small electrostatic capacities, such as those of short lengths of cable.

The instrument is formed by two mutually insulated metallic pieces, which we shall call A and B, constituting the two systems of an air condenser, or, as we shall now call it, an air leyden. The systems are composed of pa.rallel plates, each set bound together by four long metal bolts. The two extreme plates of set A are circles of much thicker metal than the rest, which are all squares of thin

FIG. 1.

1892.] and Measurement of Small Electrostatic Capacities. 7

sheet brass. The set B are all squares, the bottom one of which is of much thicker metal than the others, and tiie plates of this system are one less in number than the plates of system A. The four bolts binding together the plates of each system pass through well-fitted holes in the corners of the squares ; and the distance from plate to plate of the same set is regulated by annular distance pieces which are carefully made to fit the bolt, and are made exactly the same in all respects. Each system is bound firmly together by screwing home nuts on the ends of the bolts, and thus the parallelism and rigidity of the entire set is secured.

The two systems are made up together, so that every plate of B is between two plates of A, and every plate of A, except the two end ones, which only present one face to those of the opposite set, is between two plates of B. When the instrument is set up for use, the system B rests by means of the well-known " hole, slot, and plane arrangement," * engraved on the under side of its bottom plate, on three upwardly projecting glass columns which are attached to three metal screws working through the sole plate of system A. These screws can be raised or lowered at pleasure, and by means of a gauge the plates of system B can be adjusted to exactly midway between, and parallel to, the plates of system A. The complete leyden stands upon three vulcanite feet attached to the lower side of the sole plate of system A.

In order that the instrument may not be injured in carriage, an arrangement, described as follows, is provided by which system B can be lifted from off the three glass columns and firmly clamped to the top and bottom plates of system A.

The bolts fixing the corners of the plates of system B are made long enough to pass through wide conical holes cut in the top and bottom plates of system A, and the nuts at the top end of the bolts are also conical in form, while conical nuts are also fixed to their lower ends below the base plate of system A. Thumbscrew nuts, /, are placed upon the upper ends of the bolts after they pass through the holes in the top plate of system A.

When the instrument is set up ready for use these thumbscrews are turned up against fixed stops, g, so as to be well clear of the top plate of system A ; but when the instrument is packed for carriage they are screwed down against the plate until the conical nuts mentioned above are drawn up into the conical holes in the top and bottom plates of system A ; system B is thus raised off the glass pillars, and the two systems are securely locked together so as to prevent damage to the instrument.

A dust- tight cylindrical metal case, h, which can be easily taken off for inspection, covers the two systems and fits on to a flange on * Thomson and Tait's ' Natural Philosophy,' § 198, example 3.

8 Lord Kelvin. On a new Form of Air Ley den, [June 2,

FIG. 2.

system A. The wnole instrument, as said above, rests on three vulcanite legs attached to the base plate of system A ; and two terminals are provided, one, i, on the base of system A, and the other,;, on the end of one of the corner bolts of system B.

The air leyden which has been thus described is used as a standard

of electrostatic capacity. In the instrument actually exhibited to the

Society there are twenty-two plates of the system B, twenty-three of

the system A, and therefore forty-four octagonal air spaces between

the two sets of plates. The thickness of each of these air spaces is

approximately O301 of a centimetre. The side of each square is

'•13 cm., and therefore the area of each octagonal air space is 85'1

sq. cm. The capacity of the whole leyden is therefore approximately

< 85-l/(47rXO-30]), or 990 cm. in electrostatic measure ; or I'l x ICT18

c.g.s., electromagnetic measure; or 1-1 x KT9 farads, or I'l x l()-3micro-

This is only an approximate estimate founded on a not

imute y accurate measurement of dimensions, and not corrected for

e addition of capacity, due to the edges and projecting angles of

the squares and the metal cover. I hope to have the capacity deter-

l with great accuracy by comparison with Mr. Glazebrook's

standards in Cambridge.

To explain its use in connexion with an idiostatic electrometer for

he direct mewurement of the capacity of any insulated conductor, 1

1 suppose, for example, this insulated conductor to be the

1892.] and Measurement of Small Electrostatic Capacities. 9

insulated wire of a short length of submarine cable core, or of telephone, or telegraph, or electric light cable, sunk under water, except a projecting portion to allow external connexion to be made with the insulated wire.

The electrometer which I find most convenient is my " multi- cellular voltmeter," rendered practically dead-beat by a disc under oil hung on the lower end of the long stem carrying the electric " needles " (or movable plates). In the multicellular voltmeter used in the experimental illustration before the Royal Society, the index shows its readings on a vertical cylindric surface, which for electric light stations is more convenient than the horizontal scale of the multicellular voltmeters hitherto in use ; but for the measurement of electrostatic capacity the older horizontal scale instrument is as con- venient as the new form.

FIG. 3.

To give a convenient primary electrification for the measurement, a voltaic battery, VV (fig. 3), of about 150 or 200 elements, of each of which the liquid is a drop of water held up by capillary attraction between a zinc and copper plate about 1 mm. asunder. An ordinary electric machine, or even a stick of rubbed sealing-wax may, how- ever, be used, but not with the same facility for giving the amount of electrification desired as the voltaic battery.

One end of the voltaic battery is kept joined metallically to a wire,

10 On a new Form of Air Leyden, $c. [June 2,

W, dipping in the water in which the cable is submerged, and with the case C of the mnlticellnlar, and with the case and plates A of the leyden, and with a fixed stud, S, forming part of the operating key to be described later. The other end of the voltaic battery is connected to a flexible insulated wire, FFF, used for giving the primary electrification to the insulated wire J of the cable, and the insulated cells II of the multicellular kept metallically connected with J. The insulated plates, B, of the leyden are connected to a spring, KL, of the operating key referred to above, which, when left to itself, presses down on the metal stud S, and which is very perfectly insulated when lifted from contact with S by a finger applied to the insulating handle K. A second well insulated stud, S', is kept in metallic connection with J and I (the insulated wire of the cable and the insulated cells of the multicellular).

To make a measurement the flexible wire F is brought by hand to touch momentarily on a wire connected with the stud S', and imme- diately after that a reading of the electrometer is taken and watched for a minute or two to test either that there is no sensible loss by imperfect insulation of the cable and the insulated cells of the multi- cellular, or that the loss is not sufficiently rapid to vitiate the measurement. When the operator is satisfied with this he records his reading of the electrometer, presses up the handle K of the key, and so disconnects the plates B of the leyden from S and A, and connects them with S', J, I. Fifteen or twenty seconds of time suffices to take the thus diminished reading of the multicellular, and the measurement is complete.

The capacity of the cable is then found by the analogy : As the excess of the first reading of the electrometer above the second is to the second, so is the capacity of the leyden to the capacity of the cable.

The preceding statement describes the arrangement which is most convenient when the capacity of the cable exceeds the capacity of the leyden. The plan which is most convenient in the other case, that is to say, when the capacity of the cable is less than that of the leyden, is had by interchanging B and J throughout the description. In this case, a charge given to the leyden is divided between it and the cable. The capacity of the cable is then found by the analogy:— As the second reading of the electrometer is to the excess of the first above the second, so is the capacity of the leyden to the capacity of the cable.

A small correction is readily made with sufficient accuracy, for the varying capacity of the electrometer, according to the different posi- tions of the movable plates, corresponding to the different readings, by aid of a table of corrections determined by special measurements for capacity of the multicellular.

1892.] On certain Ternary Alloys. 11

V. " On Certain Ternary Alloys. Part VI. Alloys containing Aluminium, together with Lead (or Bismuth) and Tin (or Silver)." By C. R. ALDER WRIGHT, D.Sc.. F.R.S., Lecturer on Chemistry and Physics in St. Mary's Hospital Medical School. Received May 13, 1892.

The experiments described in the previous five papers* have shown inter alia that when the critical curves are delineated deduced with lead (or hismuth) as heavier immiscible metal, zinc as lighter ditto, and tin (or silver) as " solvent," the curves where bismuth is sub- stituted for lead lie inside, and those where silver is substituted for tin outside, the original curves ; and, further, that in certain cases the formation of definite atomic compounds between particular pairs of metals leads to marked results as regards the mutual relations of the various pairs of conjugate points. Thus, silver and zinc form the compounds AgZn5 and Ag4Zn5, with the result of producing marked bulging (inwards or outwards) of the curves deduced with these two metals associated with either lead or bismuth. Tin and zinc appear to form the compound SnZn4, with the result of causing a peculiar convergence of the tie-lines when the proportions of metals mixed together permit of the formation of lighter alloys containing tin and zinc in approximately this ratio. Again, the alloys of lead, zinc, and tin are remarkable in that the lower ties slope in one direction, and the upper ones in the opposite direction ; and the position where the angle of slope of the lower ties is greatest (which is approximately the point where the excess of tin percentage in the lighter alloy over that in the heavier one is a maximum) is situated very near to that corresponding with a ratio of tin to lead in the heavier alloy denoted by the formula SnPb3.

The following experiments were made with mixtures of metals cor- responding with those previously described, excepting that aluminium was substituted for zinc. One general result appears to be that this substitution always causes the curve to lie outside of its former position ; and another, that as aluminium does not appear to unite with silver to form compounds analogous to AgZn5 and Ag4Zn5, the peculiar bulges observed with silver-zinc-lead and silver-zinc-bismuth alloys are not visible with silver-aluminium-lead and silver-aluminium- bismuth alloys.

These experiments were commenced about four years ago, at which time moderately pure aluminium was not in the market in any quantity; at least, a number of samples of metals prepared by

* Part I, < Roy. Soc. Proc.,' vol. 45, p. 461 : Part II, vol. 48, p. 25 ; Part III, vol. 49, p. 156 ; Part IV, vol. 49, p. 174 ; Part V, vol. 50, p. 372.

1-2 Dr. C. R. Alder Wright. [June 2

different makers were examined with the object of obtaining a few pounds of aluminium in the highest practicable state of purity; but, although several of these were stated to contain 98 to 99 per cent, of aluminium and upwards, on analysis far greater amounts of impurity than 1 or 2 per cent, were generally found to be present. Thus, one sample of the so-called pure metal contained upwards of 10 per cent. of iron; another contained, besides some iron, 2*05 per cent, of matters other than silicon and silica insoluble in aqua regia, and 2'91 per cent, of silicon, partly oxidised by aqua regia to soluble silicic acid, partly oxidised but not dissolved, and partly not oxidised at all. The batch finally selected as the best obtainable had the following composition, the sample being drawn from a considerable mass melted together ; it was supplied as metal of as nearly perfect purity as commercially possible to obtain, and containing upwards of 99 per cent, of aluminium :

Silicon left undissolved and unoxidised by

aqua regia 0'30

Silicon oxidised but not dissolved by aqua regia 1*01

,, and dissolved by aqua regia. .. O13

Total silicon 1-44

Iron 2-75

Aluminium (by difference) 95*81

100-00

No other impurities of any kind could be detected.*

When this metal was employed in the production of a compound ternary ingot it was found that almost the whole of the silicon and iron were contained in the lighter alloy in which the aluminium pre- dominated (as compared with the heavier alloy). In some cases, however, when the amount of aluminium in the heavier alloy became

* [At the present time aluminium containing notably smaller quantities of silicon and iron can be obtained commercially at less than one-eighth the price charged in 1S8S. Thus a recent sample of ordinary deliveries of "Neuhausen" aluminium v»as found to contain

Silicon left undissolved and unoxidised by aqua regia. ... 0 '41

Silicon oxidised but not dissolved ' 0 '07

»» » and dissolved by aqua regia 0 -83

Total silicon

Iron

Copper

Aluminium (by difference)

May 30, 1892.]

:

100-00

1892.] On certain Ternary Alloys. 13

considerable, small amounts of iron and silicon were also contained therein.

In some cases, when the amount of aluminium in the upper alloy was large and the other constituents small, the aluminium was taken by difference, the percentages being corrected by means of the above analysis to what they would have been if reckoned on the sum of the aluminium and the other two metals as 100. When, however, the other constituents were present in larger quantity the aluminium was directly determined, the alumina ultimately precipitated being col- lected and weighed, and the Si02 and Fe203 present therein subse- quently determined and subtracted so as to obtain a corrected deter- mination of the aluminium ; the percentages were then reckoned on the sum of the aluminium thus found and the other two metals as 100. Thus, for example, an alloy of tin, lead, and aluminium was found to contain 12'01 per cent, of tin and 1*71 per cent, of lead; hence, reckoning the difference, 86'28 per cent., as aluminium, silicon, and iron containing 95'81 per cent, of the first, the corrected ana- lysis is

Tin 12-01 = 12-46

Lead 1-71 = 1-77

Aluminium. . ,86'28 x 0*9581 = 82'66 = 85'77

96-38 100-00

On the other hand, an alloy of silver, aluminium, and lead was found to contain the following percentages of these three metals respectively, the aluminium being reckoned from the weight of alumina after subtraction of silica and ferric oxide contained in the mixed precipitate first weighed ; whence the annexed composition, calculated on the sum of the three metals as 100 :

Calculated on sum Found. as 100.

Silver 80'17 8079

Lead 6'55 6'60

Aluminium 12*51 12'61

99-23 100-00

In the case of the lighter alloys containing tin, aluminium, and lead (or bismuth) with large percentages of the first metal, it was sometimes found that a notable amount of oxygen was absorbed by the ingot whilst standing molten for eight hours, so that a per- ceptible deficiency from 100 was observed when all the constituents were added together. With silver-aluminium-lead and silver- aluminium-bismuth alloys this was not the case ; on the other hand,

u Dr. C. R. Alder Wright. [June 2,

alloys containing antimony instead of tin or silver absorbed oxygen still more readily. In all such cases the analyses are calculated npon the sTm of the aluminium, tin, and lead as 100 ; thus m the followmg

instance :

Directly Calculated on sum

determined. as 100.

Tin ...... 52-53 54-82

" -16 B'52

Aluminium ......... 35-12 36-66

Iron ............... 0-99

Silicon (total) ....... 0'51

Oxygen (by difference) 2'69

100-00 100-00

Mixtures of Aluminium, Lead, and Tin.

A number of ternary mixtures were prepared by melting alu- minium, and then adding weighed quantities of lead and tin, and stirring vigorously. A considerable amount of scoriae was usually formed, the lead partially oxidising, and the presence of the lead oxide formed causing the mass to " flour " considerably ; usually the molten portion was run off into an ingot mould, and then re-melted, and when in the pasty stage preceding complete fusion rubbed about in the bottom of the crucible with a hot fireclay pestle, so as to promote intermixture. Finally the temperature was raised, so as to bring about complete fusion, and after more vigorous stirring the liquid metal was poured into red-hot narrow clay crucibles or test- tubes, and maintained molten in a lead bath for seven to eight hours in the manner previously described. The temperature during this period of tranquil fusion lay between 750° and 850°, and averaged close upon 800°, as determined by the platinum specific heat pyrometer (Part I). No flux of any kind was used during the previous meltings and stirrings, oxidation being diminished as far as practicable by directing a current of coal gas into the crucible ; notwithstanding a much larger amount of oxidation usually took place than with metallic mixtures fused together with potassium cyanide, as in