superphosphate drilled with the seed would be found quite sufficient, and probably fully equal in effect to twice the quantity of phosphoric acid applied as powdered coprolite.

Phosphate of iron applied alone was found to have practically no effect on the turnip crop, and the effect of phosphate of aluminium was but little; this is pretty much as we should expect. There is apparently some mistake in the printed analysis of the phosphate of aluminium used, as it is made to contain 38 28 per cent. of lime, and only 476 per cent. of ferric oxide and alumina.

The analyses given of the turnip soils cannot pass without a word; the reporter is surely unaware of the absurdity which these analyses present. The soil of the unmanured plot in the five experimental fields was analysed in 1876, and again in 1879, after three turnip crops had been taken. The analyses show that on an average about 20 per cent. of the nitrogen, and about 48 per cent. of the phosphoric acid in the soil had been removed during these three years, and yet the total weight of the three turnip crops grown on the five fields during this period averaged but 16 tons per acre! The only remark made by the reporter on these figures is that the soil has evidently become reduced in nitrogen, and much reduced in phosphates; the fact that either the soil sampling or the analyses must be utterly wrong seems to have altogether escaped his attention.

The experiments with oats do not call for any special remark, except to note the patience which shelled 136,000 grains by hand in order to determine the proportion of kernel to husk in the produce of the various plots.

May we suggest that in a report of field experiments the dates of sowing and of harvest should always be given, and also a description of the character of the weather during the growing period. Without such facts before us it is impossible to interpret the results of field experiments.

two media between which the transition is gradual, and on the stability or instability of certain fluid motions. Mr. Samuel Roberts has two notes: one on a problem of Fibonacci's, and the other on the integral solution of 2 Py2 = 22 or 2 in certain cases; Mr. R. F. Scott writes on cubic determinants and other determinants of higher class, and on determinants of alternate numbers (a treatment which he has adopted in his work Determinants ''). Mr. Hugh McColl contributes a fourth paper on the calculus of equivalent statements (cf. Prof. Jevons's remarks, NATURE, vol. xxiii. p. 485). Other minor articles conclude the volume.

on

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts. No notice is taken of anonymous communications.

[The Editor urgently requests correspondents to keep their letters as short as possible. The pressure on his space is so great that it is impossible otherwise to ensure the appearance even of com. munications containing interesting and novel facts.]

The New Museum of Natural History

THE new Natural History Museum, opened on Easter Monday, was visited by some 16,000 people of a most orderly and respectable class. Owing to the great exertions of Dr. Woodand the Gallery of Reptiles were shown in a practically completed ward, whose zeal is beyond praise, the main gallery, the Pavilion, state. The Mineral Gallery has long been ready, but the arrangement of the botanical section is still incomplete, and it was entirely closed. Some little trouble was caused with the umbrellas, and it might be worth while to consider whether, except perhaps in wet weather, the umbrellas need be taken away. The idea that people poke with sticks at objects in museums has been long exploded, and no inconvenience is felt at the Kensington Museum, the Louvre, and nearly all foreign galleries and exhibitions, where umbrellas are admitted.

The architecture in the Mammalia Gallery is very obtrusive,

xi. (November, 1879, to November, 1880).

THIS is a smaller volume than usual, there being fewer papers, and none of them of a great length. The pure mathematics prevails somewhat more than usual over the mixed.

Prof. Cayley contributes articles "On the Binomial Equation x Io; Trisection and Quartisection," a theorem in spherical trigonometry, on a formula of elimination. Sir James Cockle writes "On a Binomial Biordinal and the Constants of its Complete Solution." Mr. J. W. L. Glaisher, "On a Method of obtaining the q-formula for the Sine-amplitude in Elliptic Functions"; Mr. H. W. Lloyd Tanner, “Notes on a General Method of Solving Partial Differential Equations of the First Order with several Dependent Variables," and a preliminary note on a generalisation of Pfaff's Theorem ; Mr. J. J. Walker, "Theorems in the Calculus of Operations"; and Mr. T. R. Terry, "Notes on a Class of Definite Integrals." Papers of a geometrical nature are-Mr. J. Griffiths, on a geometrical form of Landen's theorem with regard to a hyperbolic arc, and on a class of closed curves whose arcs possess the same property as two Fagnanian arcs of an ellipse; Mr. H. Hart, on the focal curves of a bicircular quartic; Mr. H. M. Taylor, on the equation of two planes which can be drawn through two given points to touch a quartic; Rev. J. Wolstenholme, a form of the equation determining the form and directions of a conic whose equation in Cartesian co-ordinates is given. Dr. Klein of Leipsic has a short note on the transformation of elliptical functions; Mr. Greenhill applies elliptic co-ordinates and Lagrange's equations of motion to Euler's problem of two centres of force; and Mr. Routh writes on functions analogous to Laplace's functions. Lord Rayleigh's papers are on reflection of vibrations at the confines of

terra-cotta, and the similarity of this in colour to the skulls and skeletons of the fossil mammalia, are most unfortunate.

It seems a pity that some style with more repose than "Decorated Norman was not selected. Although very beautiful as a building, and with many features de erving high praise from an architectural point of view, it is evidently not the style best adapted to set off natural history specimens. The cathedral like Index Museum, with its rather dark side-chapels, and the Museum of British Zoology are of proportions that will render it difficult to make an effective display in them.

I hope that it is not finally decided to place the recent mammalia on the first floor and the birds on the ground floor, because the architect's string courses would be interfered with otherwise by the cases. The living and extinct mammalia should face each other, and the birds go aloft. Convenience has already been too much sacrificed to architecture. Every time the first floor is visited the length of the Index Museum, 150 feet, must be traversed to reach the stairs, and the same distance back along the corridor to reach the door of the Mineral Gallery. This means an immense waste of time. I also notice that the crane is close to the main entrance, and that there are no proper lifts.

If it was necessary to fashion all the ornaments from naturalhistory objects, it is a pity that the restorations were not accurately made. The oft-repeated figure of a Dapedius swallowing a fish almost its own size, and of spiral shells bent to accommodate them to the mouldings of an arch, is not instructive. with a hideously-represented Archeopteryx in high relief, reThe humour of ornamenting (?) the arch leading into the pavilion peated a dozen times, is not obvious, but some joke must doubtless be intended.

The cost of the small bronze and glass conservatories in the botanical department is out of all proportion to the objects they are to contain. Dried stems of tree-ferns and palms, though very interesting in their way, do very well in other museums without glass cases, and can be replenished for next to nothing.

F. G. S.

The Tide-Predicter

MR. EDWARD ROBERTS' letter in NATURE for April 14 contains statements giving an erroneous view of the origin of the tide predicter. Any one who feels sufficient interest in the subject to derive full information will find it in my paper on "The Tide-Gauge, Tidal Harmonic Analyser, and Tide-Predicter," read before the Institution of Civil Engineers on March 1 and in the abstract of the discussion which followed it, to be published in the Minutes of the Proceedings of the Institution (vol. lxv. sess. 1880-81, part iii.), and he will see that my letter in NATURE of March 31 is correct. WILLIAM THOMSON

The University, Glasgow, April 16

Geological Relations of Gold in Nova Scotia IN the notice of the report of Mr. Murray on the gold of Newfoundland (NATURE, vol. xxiii. p. 472) I observe a reference to my own opinion of the age of the gold of Nova Scotia which needs some correction. In the second edition of "Acadian Geology" (1868) the gold-bearing series is included in the Lower Silurian, but this referred to the larger sense of that term in which it was used to include the Cambrian as well. In the third edition (1878, Supplement, pp. 81, 85, 92) I have referred this formation, on the evidence of fossils and stratigraphical position, to the age of the Lower Cambrian or Longmynd series, thus placing it on a lower horizon than the fossiliferous Primordial of Eastern Newfoundland, which I suppose to be of the age of the Acadian or Menevian group. There is therefore little difference between Mr. Murray's estimate of the age of the gold-bearing rocks of Newfoundland and my own of that of the similar rocks in Nova Scotia, except that I presume he would classify the Newfoundland series as Upper Huronian rather than Lower Cambrian. With reference to this I have been disposed to regard Mr. Murray's Aspidella slates and the associated rocks as equivalents of the Kewenian or "Upper copper-bearing group" of the West, and probably Upper Huronian, in which case they might be a little below my Nova Scotia Lower Cambrian; but the precise age of both series is determined merely by the fact that they appear to belong to the period between the Huronian proper, or Lower Huronian, and the Acadian group, or Menevian (Etage C. of Barrande).

It is proper to add that in the third edition of "Acadian Geology" I have shown that the filling of the Nova Scotia gold veins is much more recent than the containing rocks, and belongs to the time intervening between the Upper Silurian and the Lower Carboniferous, the richer deposits also appearing to be related to the occurrence of intrusive granites of Devonian age. There is no reason, therefore, other than the mineral character of the containing beds, why such veins might not occur in any rocks older than the Devonian, and gold discoveries have been reported in localities where the rocks are supposed to be Huronian and Silurian; but I have had no opportunity of personally verifying these statements. Thus far the important gold veins are known only in that great series of slates and quartzites of the Atlantic coast which I have referred to the Lower Cambrian. J. W. DAWSON

McGill College, Montreal, April 4

Symbolical Logic

PROF. JEVONS, in his criticism of my method in NATURE, vol. xxiii. p. 485, has stated the main points at issue between us so fully and clearly, and on the whole so fairly, that I need only say a very few words in reply.

As to the charge that my method is ante-Boolian or antiBoolian, I do not seek to repel it; on the contrary, I maintain that my method is different from Boole's in principle, and very different indeed in its practical working. The really important questions to be settled are these:

I. Are the definitions which I give of my symbols clear and unambiguous?

2. Are the rules and formula which I derive from these definitions correct?

3. Are the innovations which I propose of any practical utility?

Now, I do not think that any one who has read my papers in the Proceedings of the London Mathematical Society and my articles in Mind and in the Philosophical Magazine will refuse to answer Yes to questions I and 2; and with regard to question

3 I can only say that any one who answers No is bound in fairness to prove the inutility of my innovations by solving one or two of my hardest problems without their aid, and in an equally clear and concise manner. My proposal of an amicable contest

in the Educational Times meant nothing more serious than this. Some of my critics (not including Prof. Jevons however) seem anxious to magnify the points of resemblance between my method and its predecessors, especially Boole's, and to minimise the points of difference. It may be as well therefore to state briefly what characteristics distinguish my method, so far as I know, from all the methods which have preceded it, and what advantages, in my opinion, accompany these characteristics.

In the first place, then, every single letter in my notation, as well as every combination of letters, denotes a statement. By this simble device I gain the important advantages of generality of expression and uniformity of interpretation and treatment. It enables me to express many important logical laws in simple and symmetrical formulæ, as, for instance,

(A: a) (Bb) (C : c) : (A + B + C: a + b + c), which otherwise could not be so expressed. To secure these advantages I sacrifice absolutely nothing. The relations of classes, including the ordinary syllogisms, I express by speaking throughout of one individual, just as mathematicians express the properties of curves, surfaces, and volumes, by speaking throughout of the varying distances of one representative point.

My claim to priority on this head has been called in question on the ground that Boole too, in his equations about "secondary propositions," denotes statements by single letters. The plain truth however is that Boole takes some pains to prevent his readers from imagining that he does anything of the kind. He says distinctly, and in perfect consistency with the whole tenor of his book, in which he describes his algebra of logic as a mere offshoot and part of the ordinary algebra of quantity, that in his equations any single letter, such as x, denotes the portion of time during which some proposition x is true, the whole universe of time to which the discourse refers being the unit (see “Laws of Thought," from p. 164 to p. 170). Neither will one find anywhere in Boole's work the idea (suggested to me by analytical geometry) of investigating the relations of different classes, while speaking only of one individual, and thus dispensing entirely with the quantitative words all, some, and none, which are so characteristic of the old logic.

Another peculiarity of my method is that my symbol of denial (an accent) is made repeatedly to apply to expressions of varying complexity, as, for instance, (xy)', (x + y z)'. (x : y')', leading to rules and formulae of operations, to which I find no parallel in any prior symbolic system with which I am acquainted.

Boole uses x as an abbreviation for I - x. Let those who insist that Boole's horizontal stroke is exactly equivalent to my accent express in his notation the complex equation

(x = y)' = (x : y)' + (y : x)',

and explain its meaning clearly without departing from Boole's quantitative interpretation of his symbols.

Lastly, my symbol: expresses implication or inference, and does not, therefore, exactly coincide in meaning with Prof. Peirce's symbol of inclusion —<, as defined by him in his "Logic of Relatives," published in 1870. This symbol of inclusion, as I understand Prof. Peirce's definition of it, is simply equivalent to the words "is not greater than," and is therefore restricted to number and quantity. It is true that Prof. Peirce in his recent memoir on the "Algebra of Logic" extends the meaning of this symbol of inclusion, so as to make it also convey the same meaning as my symbol of implication; but as this memoir was published subsequently to my second and third papers in the Proceedings of the Mathematical Society, to which Prof. Peirce explicitly refers in his memoir and accompanying circular note, this later definition does not bear upon the point in discussion.

Prof. Jevons objects to my a: B as an abbreviation for a a B, because he thinks it obscures the real nature of the reasoning operation. But one might with equal justice object on the same grounds to a3 as an abbreviation for aaa, or to the left side of the equation in the binomial theorem as an abbreviation for the right side. The symbol a: B is the exact equivalent of a = a ẞ, just as a = 8 is the exact equivalent of (a : 8) (B: a), and I do not see that I create any obscurity by adopting in any investigation, and at any stage of the investigation, whatever form seems most suitable for the immediate purpose in view. But whether I am right or wrong in this opinion can only

be decided by actual examination of my published papers on symbolical logic, of which Prof. Jevons has very kindly given in NATURE a full and complete list. HUGH MACCOLL 73, Rue Siblequin, Boulogne-sur Mer, April 7

Agricultural Communism in Greece

THE article in NATURE, vol. xxiii. p. 525, on Aryan villages and other Asiatic communities reminds me of what I saw in 1843 in the course of a journey through Greece. On St. George's Day, a high festival with the Greek peasants, when crossing the range of Mount Citharon between Thebes and Eleusis, I saw my companion, who was about half a mile ahead, surrounded by a number of men, and then pulled from his horse. The man we had engaged as interpreter, guide, and protector, the "dragoman," bolted as a matter of course, thinking we had fallen upon a nest of brigands; but when I reached the scene of action I was surprised to find that the yelling and uproar heard in the distance were not murderous nor at all malignant, but purely hilarious. I was dragged from my horse also, and surrounded by about twenty young fellows with shaven heads and long scalp locks, half stripped, half drunk, and very dirty, but perfectly good humoured.

We were presently made to join in a wild dance, a survival of the Pyrrhic dance of antiquity, which we improved very successfully; my companion, C. M. Clayton, from Delaware, doing a nigger break down and I the sailor's hornpipe.

On the final arrival of our dragoman we learned that the twenty young men were brothers, and that the old man with long white beard who sat gravely looking on and playing a sort of tom-tom to tune the dance was their father. On our expressing surprise at so large a family of sons being so nearly of the same age he explained that doeλpós did not always signify a blood relation, and that these were merely agricultural brethren. They were the united proprietors or renters (I do not remember which) of the adjoining farmhouse and the surrounding land, which they cultivated under the direction of the old man whom they had selected as their father, who was entrusted with the custody and division of their capital and profits, who arbitrated in cases of quarrels, and was otherwise obeyed in most things.

Here was a patriarchal form of communism that we afterwards met with in several other instances, but in this and the other cases it was limited to young unmarried men. There were no women in the dance and none visible on this farm, which was some miles distant from the nearest village, Platea.

At that time the Klephts, or brigands, were united in similar communities, who sternly abjured all communication with the fair sex.

When we had finished our dance and paid for sufficient wine to go round the family circle we found that before going we must kiss all the brothers or give mortal and dangerous offence. Andrew, our dragoman, with the inventive facility of his nation, extricated us from this by solemnly stating that in England it was an established custom to show respect for a family by embracing the father only, and bowing separately to each of the sons.

I am unable to supply any further particulars concerning the internal economy of these communities, cannot say whether they prevail chiefly among the Greeks or the Albanians (the latter constitute a large proportion of the agricultural population of Greece), nor how they dissolve when the brothers become married or the father dies. I have met with no account of them in the course of my reading, but am not at all surprised at this, seeing how profound is our general ignorance of everything pertaining to Greece, an ignorance which is most glaringly displayed by political writers and others, who speak of Athens as though it were Greece, and of Athenian proceedings as though they were the action of the Greeks.

But for the accident of this rather startling festive encounter with these brethren on this particular holiday, we might have travelled for weeks without meeting any visible indications of such fraternities. We should have passed the brothers if they were working in the fields, and the patriarch had he been sitting alone at the farmhouse door, without special notice. It was only after our curiosity had been excited that we discovered other patriarchs and other brethren by special inquiry where their existence was vaguely indicated.

Among the readers of NATURE there may be some who have sufficient acquaintance with the Greek people, outside of Athens, to be able to supply interesting particulars concerning these

curious communities. They may be survivals of our ancient communism, or a modern device for mutual protection forced upon the rural population by the absence of any enforcement of law and social order by those who consume the taxes in Athens. W. MATTIEU WILLIAMS

Heat of Stellar Masses

I SEND you a working hypothesis which I think will well pay for its place in the world. It is as to the heat of large stellar masses; that the imperfect conduction of the kinetic force producing gravitation through large stellar masses causes heat in them.

The quantity of heat stored up may depend partly on the proportion of mass to radiating power, and partly, perhaps, on the condition of the mass for such conduction. Washington, D. C., March 25 SAML. J. WALLACE

Shadows Cast by Venus

ON March 21 last, about 8 p.m., I was walking among some trees by a river's bank. The ground was covered with recently. fallen snow, and the shadows of the trees were unmistakably, though faintly, traceable on the white surface. The night was dark and the shadows were thrown by Venus, which was shining with unusual brilliancy. I believe this obvious form of the phenomenon is not a common one in our latitude. CHAS. T. WHITMELL

31, Havelock Street, Sheffield, April 18

The Sparrow and Division of Labour THE following curious fact may possibly interest your ornithological readers :- Last year and the year previous two pairs of swallows made their nests and successfully reared their broods under the eaves of my house. Within the past fortnight a brace of astute London sparrows have apparently recognised the principle of division of labour as applicable to their requirements in the art of nest-building. They have selected the largest and most substantial of the swallows' nests referred to; and, after devoting a day or two, on starting on their enterprise, to the enlargement of the entrance hole, which was probably too narrow for them, have constructed their bed within of bits of grass and feathers in the usual fashion. They are now enjoying their honeymoon in their new quarters. G. C. WALLICH

3, Christchurch Road, Roupell Park, April 11

SIR PHILIP DE MALPAS GREY EGERTON,

M.P., F.R.S.

IN N Sir Philip Egerton geologists have lost one of that band of workers who placed their science upon the footing which it now occupies in this country. Unfortunately that band has been of late years greatly diminished by death. Born in 1807, Sir Philip Egerton with his old friend and fellow-worker, Lord Cole (now the Earl of Enniskillen), while still at Oxford commenced the collection of fossils, and very soon their attention was especially directed to fossil fish, of which but very little was at that time known. As specimens of this group of organisms often occur in duplicate, the individuals breaking across so that two opposite slabs each contain one-half, the two friends agreed to share their spoils, and thus both collections were enriched. When in 1840 Agassiz visited this country, intent upon his great ichthyological memoirs, he found in the museums of Sir Philip Egerton and Lord Cole an abundance of materials ready to his hand. The specimens were carefully figured, and descriptions of them included in the several great works which Agassiz successively issued. The original drawings by Dinkel are now among the archives of the Geological Society. But Sir Philip Egerton was by no means merely a collector of fossils, he was a very diligent and successful student of ichthyology. Many valuable papers on fossil fishes were written by him at different times, and a series

of papers published in the decades of the Geological Survey of the United Kingdom are among the most valuable of the works issued by that body. An excellent man of business, Sir Philip took an active part in the administration of the British Museum, the London University, the Geological Society, and other institutions for the promotion of science. All who knew him will miss the kindly face and cheerful manners which distinguished him. Only two days before his death he was in his place in Parliament, but a chill caught during the lately prevalent east winds proved rapidly fatal. At the last meeting of the Geological Society the vice-president, Mr. J. Whitaker Hulke, F. R.S., made announcement of his death, and the sudden and unexpected tidings concerning one who was so widely known and so universally respected cast a sad gloom over the proceedings of the evening.

A correspondent sends us the following additional note on the late Sir Philip Egerton :

The knowledge of the extinct species of fishes is one of the latest additions to palæontology, and the creator of this department of the science, Louis Agassiz, found the richest materials for his great work in the British Isles. In their acquisition he was greatly aided by Lord Cole, now Earl of Enniskillen, and by Sir Philip de Malpas Grey Egerton, Bart., M.P. Their gatherings resulted in most complete collections of fossil fishes, and science is much indebted to the catalogues drawn up and published by Sir P. Egerton of that preserved at Oulton Park. Besides the species named by Agassiz this collection includes many which have been subsequently determined and described by Sir P. Egerton, whose name will be ever associated with that of Agassiz in palichthyology. In his public career Sir Philip Egerton has been distinguished by his unremitting attention to his parliamentary duties in the long period since his election in 1830. The British Museum sustains a severe loss in a Trustee, elected in 1851, whose scientific knowledge, sound judgment, and administrative ability were of the greatest value, especially to the Natural History Departments. Sir Philip's last attendance at the Board was but a few days-apparently in his usual good health-before his lamented death.

THE SCIENTIFIC PRINCIPLES INVOLVED IN

FOUR

ELECTRIC LIGHTING

OUR Cantor Lectures on this interesting subject have just been delivered at the Society of Arts by Prof. W. Grylls Adams, F.R.S.; the lectures will be published in full in the Journal of the Society of Arts, but we are able to give an abstract of them by Prof. Adams. In the first lecture, the discoveries of Ersted, Ampère, Arago, and the early discoveries of Faraday on magnetic and current induction were considered in their relation to the principles of conservation and transformation of energy.

Lecture I.-Prof. Adams began by stating and illustrating the fact that important discoveries, after they are made, often pass through a stage of neglect or a stage of quiet development, then enter on the practical stage, when new facts and new inventions follow with great rapidity. The potential energy of the discoverer is transformed into energy of action in many directions with more or less efficiency, according to the retarding state of the medium through which that action takes place.

Electrical science has passed through these stages, whether we regard telegraphy from the work of Sir Francis Ronalds in 1816, who said, "Let us have electrical conversazione offices communicating with each other all over the kingdom," down to the establishment of telephonic exchanges, or whether we consider electric lighting from the grand experiment of Sir Humphry Davy in 1813 with a battery of 2000 cells, down to the

latest results obtained by means of the most recent magneto- or dynamo-electric machines.

In the year 1819 Ersted observed the action of a current of electricity on a suspended magnetic needle, and in the year 1820 Ampère studied the laws of their mutual actions, and propounded his celebrated theory of magnets and of terrestrial magnetism, making magnetism the resultant action of electric currents. In the same year Arago discovered the magnetisation produced by electric currents, laying the foundation of the subject of electro-magnetism.

The discoveries of Ersted, Ampère, and Arago were fully illustrated by experiments, and their connection with one another explained. In the same year, 1820, Schweigger invented the galvanometer, and in 1827 Ohm deduced his simple theory of the action of batteries from the principle of Volta.

The relation of the experiments of Ersted, Ampère, and Arago to the principle of conservation of energy was then fully considered. Considering Ampère's experiment of the motion of wires towards one another when like parallel currents are flowing in them, it was shown that the currents must be diminished whilst they are actually approaching, and increased whilst they are separating, and so by supposing one of the original currents very small, the relation between Ampère's results and the induction of a current by moving a wire in the neighbourhood of another current was deduced.

The laws of induced currents were then explained and illustrated by some of the early experiments of Faraday, who discovered the induction of electric currents by magnets in 1831.

"In his first series of papers to the Royal Society entitled-(1) On the Induction of Electric Currents, (2) On the Evolution of Electricity from Magnetism, (3) On a New Electrical Condition of Matter, (4) On Arago's Magnetic Phenomena, Faraday unfolds step by step the laws of the induced current in a helix of wire B, placed near to another helix A, carrying a voltaic current.

"That as long as a steady current was maintained in A there was no current induced in B; that on making contact in A or on approaching the wires there was a momentary inverse current in B, and on breaking contact in A or on separating the wires, there was a direct induced current in B. That as this current was of the nature of an electric wave like the shock of a Leyden jar, it might magnetise a steel needle, although it produced slight effect on a galvanometer, and how this expectation was confirmed, and that the needle was magnetised opposite ways on making and on breaking contact." Then in his evolution of electricity from magnetism he gives an account of the greatly increased effects on introducing soft iron cores into his helices of wire, and shows that similar effects are obtained by using ordinary magnets in place of a helix carrying a battery current round an iron core, i.e., in place of an electromagnet. He then describes the experiment of introducing a magnet into a coil of wire, and shows that the same current is obtained whether the marked end of the magnet be introduced at one end of the coil or the unmarked end introduced at the other, and that a current is produced in the opposite direction to the former on withdrawing the magnet from either end. Then after describing the method of producing his induction spark and also muscular contractions of a frog by means of a loadstone and coil, and remarking that the intensity of the effect produced depends upon the rate of separation of the coil from the poles of the loadstone, he concludes this section thus: An agent which is conducted along metallic wires in the manner described; which, whilst so passing, possesses the peculiar magnetic action and force of a current of electricity; which can agitate and convulse the limbs of a frog, and which finally can produce a spark, can only be electricity.