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THE MANUFACTURE OF CYANIDES. dustrial scale. All the chief cyanide compounds are The Cyanide Industry Theoretically and Practically dealt with, and separate chapters are devoted to the

Considered. By R. Robine and M. Lenglen. manufacture of cyanides, ferrocyanides, ferricyanides, Translated by J. Arthur Leclerc, Ph.D., with an and sulphocyanides. Sulphocyanides and, to a less appendix by C. E. Munroe, Ph.D. Pp. xi x 408; extent, ferrocyanides owe their importance to their illustrated. (New York: John Wiley and Sons;

use in the preparation of cyanides, but the authors London : Chapman and Hall, Ltd., 1906.) Price devote most attention to the interesting direct syn178. net.

thetic processes of making cyanides from carbon and! THE CHE stimulating effect on industrial research nitrogen or ammonia. caused by the prospect of immediate material

The fixation of atmospheric nitrogen is a fascinating gain is strikingly illustrated by the progress of the problem which is likely to continue to exercise the cyanide industry. Until cyanide of potassium was ap

minds of chemists, and the translator, as an agriplied to the treatment of gold ores, comparatively little cultural chemist, expresses the daring hope that the interest was taken in its manufacture. The consump

publication of this volume will result in the solution: rion amounted to about fifty tons a year only, and the

of the problem on an industrial scale. It is, of course, old expensive and wasteful methods of obtaining it

well known that cyanides are formed in blast fura irum ferrocyanide which had been made by the use of naces, and many attempts have been made to apply nitrogenous organic substances were deemed sufficient this knowledge, beginning with Bunsen's special for the purpose. When the demand was rapidly grow- furnace, which was built in 1845. In most of the. ing in the 'nineties there was a rush of investigators later processes, atmospheric nitrogen, freed from to discover new and cheaper methods of manufacture. oxygen by passing it over heated metals or by disA fair amount of success was attained, and some tilling liquid air, has been passed over carbides of thousands of tons of cyanide are now produced annually metals heated in electric or other furnaces, but in Great Britain and Germany and sold at one-third although some progress has been made, the cyanide the former price. The older processes have been industry still continues to depend on more roundabandoned and new ones introduced, and, although about chemical actions. One of these is the synthesis. some doubt still remains as to the future of the of sulphocyanide by the action of ammonia on carbon industry, the field for useful research has been nar- bisulphide in the presence of a base such as lime, fol-rowed, and once again offers little attraction to the lowed by the reduction of the sulphocyanide by means. chemical “pot-hunter." Comparatively little cyanide of carbon, metals, or hydrocarbons. is produced in France, however, and apparently it Illuminating gas and its residues constitute a source was the apathy of their fellow-countrymen on the sub- of cyanide which has not been fully exploited. The ject which induced MM. Robine and Lenglen to write authors anticipate that in the future a large prothe book which has just been translated.

portion of the required cyanides will be obtained The authors divide their book into four parts, of from gas works, and estimate that in France alone. which part iii., on the methods of manufacturing 4,000,000 tons of coal used annually in the manucyanide compounds, is alone of any real importance. facture of illuminating gas could be made to yield

Part i., occupying sixty-five pages, deals with the cyanide compounds worth from eight to twelve chemistry of cyanogen and its derivatives. It con- million francs, all of which is now lost. In other tains no correct statement that does not appear in countries, however, the matter has not been overordinary text-books of chemistry, and is distinguished looked, and it is certain that the illuminating gas. by an extraordinary number of misprints or mis- used in the world could be made to yield far more statements, such as “cyanogen does unite cyanide than could possibly be disposed of, unless directly with hydrogen," "it (cyanogen] becomes a new uses for cyanide should be discovered. liquid at 200.7 under ordinary pressure,” and “ If the gress of the cyanide industry is checked rather by cyanide contains chlorides, the method (of estimation well-founded fears of overstocking the market than of cyanide by means of silver nitrate] is not accurate.” | by the neglect by manufacturers of their opportunities. There are no references to the sources of information, or by the need of fresh sources of supply. and the whole section seems to have been drawn up In part iv., which occupies twenty-seven pages,. in a perfunctory way.

there is an adequate account of the use of cyanogen Of even less value is part ii., which occupies twelve compounds, and this is followed by an appendix of pages, and is on “The Present Condition of the seventy-one pages. Here a digest is given of the Cyanide Industry." None of the information given United States patents relating to eyanide processes forin this part appears to be of later date than 1901, the recovery of the precious metals. No doubt the and some of the tables of figures end in 1896. The list is fairly complete, but it has nothing to do with tables refer mainly to France, but there is a list of the main subject of the book, and does not contain works producing cyanide compounds which applies any reference to patents relating to the manufactureto the whole world.

of cyanides. However, as it shows the activity of Part iij. occupies 213 pages, and gives a clear the consumers of cyanide, it may be taken as a tonicaccount of a very large number of methods of manu- by disheartened manufacturers, who, after all, are facture, most of which, as the authors are careful probably more interested in markets than in chemical! to point out, have never been successful on an in- formulas.

T. K. Rose.

not

The pro

van

THE

across

A YEAR ON THE SIBOGA."

student days, “Wallace's Line”-a picturesque and

fruitful hypothesis, for all the contempt with which Ein Jahr an Bord 1.M.S. Siboga. Von Frau A.

it is apt to be treated nowadays. On the other hand, Weber Bosse. Beschriebung der Holländ

interesting soundings of considerable depth were obischen Tiefsee-Expedition im Niederländisch-In

tained among the islands—some 2700 fathoms in the dischen Archipel 1899–1900. Nach der II Auflage

Banda Sea and in the Celebes Sea, 2200 fathoms in aus dem Holländischen übertragen von Frau E.

the Ceram Sea, 1500 fathoms between the Banda Ruge-Baenziger. Pp. xiii + 370. (Leipzig: W.

Sea and the Flores Sea, and 2000 fathoms close to Engelmann, 1905.) Price 6s. net.

land off Saleyer. Near the latter island great banks IN N this book Mrs. Weber gives a popular account of calcareous algæ were found, which recalls Stanley

of the expedition the scientific results of which Gardiner's observations on the importance of these have been described in the “ Siboga-Expeditie " edited organisms in Funafuti and elsewhere. The plankton by Dr. Max Weber.

also seems to have been unusually rich and plentiful. The Siboga, a twin-screw vessel of the Royal Dutch The sea bottom is in many places rough, entirely unlike vy, built for the East Indian servic deprived of

the oozy bed of the great oceans, and was the cause her armament, and specially fitted for her scientific of much loss and damage to gear. voyage, left Surabaya, on the north coast of Java, The book is well got up and illustrated by some on March 7, 1899, and returned thither on February good photographs, and should prove interesting to 26, 1900, having spent the interval-practically a year the large class of readers who are attracted by books --in exploring the marine, and especially the deep- of travel. water, fauna of the East Indies. The expedition consisted of Prof. Max Weber and Mrs. Weber, two scientific assistants, a doctor, and a draughtsman,

YORKSHIRE FUNGI. and received from the naval staff of the vessel those The Fungus Flora of Yorkshire. By G. Massee and ungrudging and invaluable services which the officers

C. Crossland. Yorkshire Naturalists' Union of our own Navy so invariably put at the disposal

Botanical Transactions, vol. iv. Pp. 396. (London: of the scientific members of an expedition. The in

A. Brown and Sons, Ltd., 1905.) vestigation of the marine flora was in the hands of

THE Yorkshire Naturalists' Union has held and Mrs. Weber.

maintained a high place in the history of British The course of the Siboga lay at first along the cryptogams, and its published Transactions abound coasts of the Lesser Sunda group from Java to

in records of fungi in which the county seems to Timor, then

the Flores Sea to Saleyer be peculiarly rich. It is hardly surprising, therefore, Island, and to Macassar, in Celebes, where the ex- that a scientific society of such well-proved eminence pedition was landed for a time while the ship made

should every now and then issue the results of its a trip to Surabaya. On her return the voyage was labours, originally published in its serial journal, in continued through the Macassar Straits to the Sulu

the form of a separate book. Islands, then southwards across the Celebes Sea to

To do this in the case of the fungi required more Kwandang, in Celebes, northwards again

to the

initiative and enterprise than with most other cryptoSangir and Talaur groups, southwards through the gams, and the committee is to be congratulated, not Molucca Straits to Obi, and eastwards across the only on having carried the work through, since 1902, Halmahera Sea to the coast of New Guinea. From but on having done it so thoroughly and efficiently. Atjatuning, in New Guinea, the ship sailed by Ceram,

When we extend our congratulations also to the Amboyna, Buru, and Buton to Saleyer again. Here two authors responsible for the work, we may take the expedition was left during a second trip of the the opportunity of pointing out that while one is Siboga to Surabaya. When a fresh start was made an amateur field naturalist of that peculiarly enthe course lay eastward across the Banda Sea by thusiastic and accurate type for which Yorkshire Amboyna to Aru and back to Amboyna. From this has long been famous, the other is a professional place the Siboga returned to Surabaya along the mycologist of high reputation; and the combined Sunda Islands by a different roure from that which labours of the two give us all the advantages of the she had taken at starting.

accurate and industrious notes of a collector who The story of this voyage is pleasantly told by knows his county thoroughly, together with the Mrs. Weber. Scattered through her account of the critical supervision of one who knows his herbarium everyday life of the ship and the happenings at equally well, and who has had shed on to his shoulders various stopping-places and dredging-grounds are the cloak of Berkeley, and has been a fellow-worker allusions to the scientific discoveries of the expedition. with Cooke. Some of the soundings are particularly interesting. The book consists of 365 pages with appendices and It appears that the Lombok Straits, instead of being an index, a too meagre bibliography, and more than a deep cleft between Bali and Lombok, are in reality 2600 entries. There is a short introduction and classifica. quite shallow (170 fathoms). Since Weber has tion, with notes on the distribution within the county. already shown that the fauna of the East Indies The work is by no means a mere catalogue, though changes only gradually from an Asiatic to an Aus- in many cases little more than the record of the name tralian character in an easterly direction, we have is given, together with the localities in which the now probably heard the last of that old friend of our fungus has been found growing. Interesting notes to the habit of the fungus abound, and while it steel works, and is also very misleading to a student is, of course, impossible in such a work to define of the subject. The matter has been dealt with in

recent and ancient literature. species or even genera, there are excellent explanatory

To sum up, the work may be of considerable interest notes here and there for the use of the critical

to the general reader, but can hardly be recommended Istematist.

as a guide to the technical man engaged in such work The volume, which is neatly printed, is, in spite of as the manufacture of steel. rather too many misprints, indispensable to every On Models of Cubic Surfaces. By W. H. Blythe. professional mycologist, and will, of course, be the Pp. xii + 106. (Cambridge : University Press, 1905.) basis for all other fungus floras of Yorkshire and

Price 4s. net.

MR. BLYTHE has attempted a difficult task, to give an other counties.

account of methods of constructing models of a cubic The work affords a very good example of the ex- surface without either assuming all the theory of the Cilent services to science which may be contributed surface as known or recapitulating it; the result, so by the collaboration of individual workers who are far as the introductory portions of the book are con+ xperts in different departments and will join their cerned, is an unsatisfying mixture of rudiments and

quotations and references to difficult theorems. As irres loyally for the benefit of the rest.

regards the latter portion Mr. Blythe may best speak Of course, it is not claimed that all the fungi of for himself. “ About ten years ago my attention was the large area covered are recorded, and much remains drawn to arranging the twenty-seven straight lines. for other workers, especially in the domain of the After constructing several models, I did not consmaller and lower fungi; but, as has already been

tinue the series, for I subsequently found that a compointed out, we have a firm basis for the benefit of plete set had been made in Germany. Copies of

these models can be purchased. Still the models further workers, and shall hope to see the records described in this book are sufficient to give an idea of gradually rendered more and more complete.

the shape of a cubic surface.

We think Mr. Blythe is too modest, and that this

little book of a hundred pages will be of interest to OUR BOOK SHELF.

those who are studying the surface and desire actually

to make models; but it must be confessed that in I ke Principles and Practice of Iron and Steel Manu

our opinion the writer would have been better advised facture. By Walter Macfarlane. Pp. xi +266; either to make the theoretical portions more systematic h figures. (London : Longmans, Green and Co.)

or to have omitted them, and given a fuller account Price 3s. 6d. net.

of the models with many more figures. Perhaps it is This is a difficult book to review so as adequately to fair to say that Mr. Blythe's book is a good example represent the nature of its contents to the “technical

of what may in cases be the bad effects of a too rigid students, metallurgists, engineers,” and others for and uniform examination system; it happens that cubic whom it is intended. The somewhat florid style of surfaces are outside what is regarded as the norma! the introduction, “ Machinery ponderous and powerful

course of geometry for a student for the mathematical of nimbly delicate and deft. :." would lead one to

tripos; under a free and stimulating system, when Mr. espect a kind of poetic phantasy woven to give joy to Blythe first began to take an interest in models of the general reader, and the expectation is supported by cubic surfaces he would have been encouraged by his the last sentence, about iron being the Master Metal environment to go on and make a complete set, and H«cause it has so many good qualities in well-balanced

other students would have helped him, and there gruportion. Really it is quite human), however, in would have been formed a fresh rootlet for the mathethat it has many wicked ways also, well known to the

matical school to grow from; as it is, the environaforesaid engineers.

ment requires either that he should invent a comLater in the work there is a compound of the pletely novel theory of the surfaces or models, or pav Pneral and the technical, as is evidenced by the type

the penalty of being regarded as off the track, except of illustrations, numbering about a hundred, of which

by those few who value mathematics as they find it considerable proportion are reproductions from interests them. photograph; thus, Fig. 6, Charging, a puddling A Synonymie Catalogue of Homoptera.

Part i. furnace”; “ Fig. 44, Siemens casting pit with ladle in the distance," evidently taken with a short-focus

Cicadidæ. By W. L. Distant. Pp. 207. (London : lons, for the ladle seems about half a mile away;

Printed by Order of the Trustees of the British "* Fig. 54, Shovelling lime into

Museum, 1906.)

steel melting furnace"; while “ Fig. 52, Empty steel ladle,” may

MR. W. L. Distant has for many years made a study be introduced to finish with a little humorous touch.

of the Rhynchota, and has paid particular attention to Taking at random the working of an acid open-hearth

the Cicadidæ. The catalogue of this family, together charge, the author says that after melting (p. 117)

with a synopsis of the subfamilies and genera now “Oxidation steadily proceeds. In the first iwo stages published, was, we learn from Prof. E. Ray Lanthe oxidation is effected by the excess air which enters

kester's preface, generously placed at the disposal of the furnace along with the producer gas.

The

the Trustees of the British Museum by Mr. Distant. oxidised products SiO,, MnO, and some Feo and

This work should be of great assistance to students Fe,, go into the slag. In the third stage oxidation

of this group of insects. in largely due to the oxygen in the ore which is Iona. By Elizabeth A. McHardy (Mrs. Raymond tid in."

122 the author distinctly says, Smith). Pp. 48. (Glasgow : R. Gibson and Sons, During the third or boiling stage when this Ltd., n.d.) Price is. net. at it is reached ore is cautiously fed into the Tuis attractive booklet provides brightly written and furnace ." How long it would take an ordinary well illustrated accounts of lona-“the Blessed Isle" charze to come on the boil without ore one could | - and of Staffa with its wonderful Fingal's Cave, burdii guess, but to bring it on in a reasonable time together with an appreciation of St. Columba. It ruuiers vrry considerable additions of ore to get the should not be long before the little publication secures slak into proper condition. This is a grave error for a wide popularity among visitors to the west of an author who has been fourteen years in iron and Scotland.

a

On p.

LETTERS TO THE EDITOR.

A Remarkable Lightning Discharge.

The afternoon of Saturday last, June 23, was sultry. (The Editor does not hold himself responsible for opinions and it was therefore without surprise that about 8.zo p.m.

expressed by his correspondents. Neither can he underlake we observed the reflection in the clouds of lightning to to return, or to correspond with the writers of, rejected

the west and south-west, and heard from time to time

the low sounds of distant thunder ; there was no indication manuscripts intended for this or any other part of NATURE.

of the storm coming near to us until 9.30 p.m., when we No notice is taken of anonymous communications.) were startled by a tremendous explosion and a brilliant

flash of light, which, according to some observers, was Kew Publications.

continued after the explosion took place. This explosion

was, I think, the loudest that I ever heard, and the As I was responsible before I left Kew for the publi; impression on all of us was that it was quite close, and cations noticed in Nature of June 21 (p. 180), perhaps I

am told that it was heard nearly two miles off as if it may be permitted a few words of explanation.

was close at hand. The thunderstorm continued for some The Kew Bulletin was not intended at the outset to

hours after this explosion, but never came near to us. rank with scientific journals. It was started at the desire

It was not until the next morning that we discovered of Parliament for the purpose of issuing, for public use, in

the scene of the explosion of the fire-ball, if such was the formation for which there happened to be a demand, and

nature of the agent. of a commercial, or at any rate economic, kind. It was

In one part of the garden here there is a mound-the subsequently decided by the Government that it should be the vehicle for other matter, scientific or otherwise, for height-on the northern side grown over with ferns, ivy.

remains of an old greenhouse--of irregular form and which prompt publication seemed desirable. It is sent out to all the botanic and agricultural depart- ash tree of moderate size, which gives out its first branches

and weeds, from which, towards its western end, grows an ments in correspondence with Kew in India and the

between 16 feet and 17 feet from the ground. The leaves colonies, and much of its contents is usually reprinted in

of the tree seem intact, but the ivy of the trunk, from the local journals.

immediately below the branches down to the mound, has It also serves the purpose of expeditiously answering been more or less stripped of its leaves; a space half round inquiries at home. A stock of the numbers is kept at Kew

the tree has been disturbed, and the weeds and plants for communication to correspondents. So useful has it

thrown down, very much as if they had been trampled proved in this way that it has been necessary to reprint down by human feet; and this disturbance is continued more than once a large number of the articles. The out

in a line down the mound on the northern side, the plants put in any one year may have been exiguous; but if there being depressed from above downwards, and the gravel was no urgent demand for information on some new sub-path at the foot of the mound broken up more than halfjects, there was usually more pressing work on hand than

way across. Many of the leaves of the ivy have been the mere manufacture of padding. As, however, the

scattered about, and many of the leaves lying on the Bulletin is filed in many libraries, I was glad to have the

mound have been torn to pieces. Several pieces of dead leisure to put the successive annual volumes into a ship wood on the mound have been broken asunder. A branch shape form. When the next general index is issued the

of ivy close to the root of the ash tree has been stripped whole series of volumes will form a sort of rough, though of its bark; an o!d brick lying on the mound under the necessarily incomplete, encyclopædia of practical inform- vegetation was broken into four pieces, two small pieces ation on Indian and colonial agriculture and products.

and two large of nearly equal size ; one of these larger The announcement of appointments may have been be- pieces was found on the mound, one was found about lated, but that again is of little consequence, as they are

7 feet 6 inches from the point at the foot of the mound only intended to be items in a continuous record.

where the disturbance was seen, one smaller piece was about The catalogue of portraits was not supposed to be ex

7 feet beyond this, and another yet 2 feet further beyond haustive, and does not compare, therefore, with the “ Cata

the last. A piece of highly-crystallised Old Red Sandstone logus Stockholmiensis. It is simply a hand-list for the lying on the mound was found with a new and unweathered use of visitors of the portraits exhibited in Museum No. 1.

exposure several inches in length, and fragments of the The Kew collection has always been popular, and, as I

same stone with new faces were lying near. know of no other, is “ probably unique," but it has latterly The conclusion from these facts seems to to be grown out of all bounds. As the available space was re

that the electric agent, whether a fire-ball or not, must stricted, I made a selection, and, so far as prints were

have approached the ash tree in a nearly horizontal line concerned, had them uniformly framed. I was guided by

and struck it just below the lowest branches, have pastel considerations which I have stated in the preface, and I down the tree to the mound, have disturbed the vegetation confess I was largely influenced for the purpose of public to the south of the trunk of the tree, have passed then exhibition by artistic merit. Mere trivial photographs and towards the north down the mound, and then to have cuttings from illustrated papers, though valuable so far as

nearly crossed the garden path, when it disappeared they go, seem to me most conveniently preserved in port- When exactly the explosion took place I feel at a loss to folios.

ascertain, but perhaps some of your readers may be able The personality of those who have made a mark in

to assist in determining this point.

Epw. FRY. scientific history has, I think, a peculiar, because intimate, Failand, near Bristol, June 25. interest. The world is certainly the poorer for having no portrait of Gilbert White. Only recently I have seen the posthumous portraits of two distinguished men of whom

The Magnetic Inertia of a Charged Sphere in a Field no memorial now remains which bears the impress of

of Electric Force. vitality.

Dr. O. HEAVISIDE has investigated (NATURE, April 19! In the seventeenth and eighteenth centuries few men the slow motion of a charged conducting sphere through of any note disdained to transmit their portraiture to a uniform electric field, in a direction parallel to the posterity by the aid of the engraver. It was not, indeed, electric force of the field, and has calculated the increase until the middle of the last century that the practice expired in the magnetic energy and inertia of the sphere resulting in the more feeble art of the lithographer. Some examples from the re-distribution of the charge under the influence of its decadence I felt obliged to withdraw as painful of the field. His paper has suggested the following in. caricatures. Nowadays, modesty or indifference seems to vestigation, in which the slow motion of the sphere is leave neglected all but the most eminent. I am not with- at right angles to the direction of the electric field. But, as out hopes that more space may be found at Kew for Dr. Heaviside has pointed out to me, this problem has no portraits. I hope the collection may continue, as in the single definite solution. For, if the sphere, initially a! past, to be the recipient of gifts from private liberality, rest in the field, be set in motion, the motion of and that in this way many obvious gaps may be filled up. the unequally distributed charges on the surface of the

W. T. THISELTON-DYER. sphere will tend to give rise to magnetic force in the Witcombe, Gloucester, June 25.

interior ; but the magnetic force will only gradually pene.

me

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trate into the interior, and electric curents circulating in where, if we use C.G.S. electromagnetic units, we have the sphere in parallel planes will cause a magnetic force u=1 and c=(3 X 10")-2. opposed to that due to the moving charges. If the con- Infinite Conductivity.-In this case a system of currents ductivity be perfect, these currents will persist, and the flows round the sphere, on its surface, in planes normal interior of the sphere will be permanently free from either to the axis of 2, the distribution being such as to give electric or magnetic force; but, with finite conductivity, rise to a magnetic potential - ucFz at internal points. the currents will die away, and the magnetic force will The magnetic force due to these conduction currents then finally attain a definite value inside the sphere, although neutralises, at internal points, the magnetic force – ucF the electric force vanishes. In each of these cases a solu- due to the moving charges. The external magnetic force tion is easily found; but while the currents are dying away due to the conduction currents will satisfy Laplace's the magnetic energy gradually changes, and the calculation equation for very slow speeds, and must, therefore, be of the energy at any given time might be difficult. I expressible in zonal harmonics, while, for all speeds, the therefore confine myself to the two limiting cases. The magnetic force normal to the sphere must be continuous. case of the final stage when there is finite conductivity | If z/r=cos y, the normal force at points just inside the I had solved when Dr. Heaviside suggested to me that sphere is ucF cos 4. The conditions are satisfied by the I should include the case of infinite conductivity in my external potential investigation. The present communication is the outcome

N=ucFacos \/27" = uc Faz/2r3, of that suggestion.

The sphere is of radius a, and carries a charge at a for this is a zonal harmonic, and gives rise to the normal speed 2, which is very small compared with v, the velocity force ucF cos y at the surface. of light; the strength of the field is F, and the specific Thus, at external points, inductive capacity is c. I employ Dr. Heaviside's units H,= -d/dx, H = -d/dy - ucEz, Hz = dadz + ucEg, in order that my results may be comparable with his. The origin is at the centre of the sphere, and the axes

where E1, E2, E, have the values already given. We thus

find of x and y are respectively parallel to the direction of motion and to the direction of the uniform electric field. H=

zucFarz When u'v is very small, the electric force E, due to the moring sphere, is the same as if the sphere were at rest, and is therefore derivable from a potential function.

H2

275 Since there is no electric force inside the sphere, the induced distribution on the sphere produces the potential

ucQy

3

H2=
Fy at internal points, and hence produces the potential
Fa'y'yd at external points. Thus at internal points the

It will be found that xH, + yH,+zH,=0 for all values components of E are

of r, and thus the magnetic force is tangential to the E=0, E,= -F, Eg=0,

sphere, a condition pointed out to me by Dr. Heaviside. while at external points they are

Hence we find
Qx

H2=w?c
E,=

cos o sin 0(2 sin20 – I)
Eg=
Qy

{ 36 sin* o cos? o- 9 sino 0(4 cos* ¢+ sinoq) +9
go
Os

Remembering that H=o at points inside the sphere, we Ez =

find, on integration through the external space, that the

magnetic energy is Finite Conductivity, Final Stage.-In this case the mag

T = f'(MQ/674 +67uc Fa/5). netic force is entirely due to the motion of the charge on the sphere, and we have

When the quantities are expressed in ordinary units the

result becomes H,=0, H,= - UEz, H=ucE,,

T= }uo [2uQ°/30 + 3uc2F%a3/10). and thus H’= u*c*(E,” + E,?). lí, now, we write

If an electron be a conducting sphere of radius 10-13 cm.

with a charge of 10-20 electromagnetic units, an electric x=rcos e, y=r cos o sin 0, z=rsin o sin 0,

force of a billion volts, or 102° C.G.S. units, per centiwe find that for internal points H’=uoc-F?, and that for metre, would not change its magnetic inertia by so much external points

as one part in ten billions, and the results are of no con

sequence in experiments on the electrostatic deflection of o

kathode rays; but it is possible that there are other cases

where it would be necessary to take the change of magF246

netic inertia into account.

When u becomes comparable with v, the analysis be

comes more complicated, but does not present any difficulty, The magnetic energy is fu H' per unit volume, and thus at least in the final stage, with finite conductivity, provided the total magnetic energy is

a Heaviside ellipsoid be substituted for a sphere.

In conclusion, I desire to acknowledge the help I have H?,? sin 0 dr de 10, received from Dr. Heaviside's suggestions, and to thank

Mr. Norman R. Campbell for verifying the formulæ. here , ranges from a to infinity, $ from o to 27, and

G. F. C. SEARLE. @ from o to r. On effecting the integration, we find Te\u(MQ2/61a + 167 ucFoao/5)= }mu,

The Date of Easter. whrpe m is the magnetic inertia.

That the formula of Gauss for finding the date of For motion parallel to F instead of right angles to it, Easter fails in certain cases, of which the year 1954 is Dr. Heaviside finds (NATURE, April 19)

one, was pointed out by Gauss in his original paper in the T = "#" [6Q4/67a+ 8#ucF?a?/5).

Monatliche Correspondenz (vol. ij., p. 129), where he shows When the quantities are measured in ordinary units the

that there are the following two exceptions to the formula results become

in the Gregorian calendar :

(1) When the formula gives April 26, Easter falls on T= 2Q/3a + 4uiF'49/51

(Searle) April 19. and

(2) When the formula gives d=28, e=6, while u M+11 T = } [24Q/3a + 2 uc?F?a/5). (Heaviside) divided by 30 gives a remainder smaller than 19, then

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