"When several of these birds combine they are very bold. A friend told me that while voyaging on the Paraná River a black-necked Swan flew past him hotly pursued by three Caranchos; and I also witnessed an attack by four birds on a widely different species. I was standing on the bank of a stream on the Pampas watching a great concourse of birds of several kinds on the opposite shore, where the carcass of a horse, from which the hide had been stripped, lay at the edge of the water. One or two hundred Hooded Gulls and about a dozen Chimangos were gathered about the carcass, and close to them a very large flock of Glossy Ibises were wading about in the water, while amongst these, standing motionless in the water, was one solitary white Egret. Presently four Caranchos appeared, two adults and two young birds in brown plumage, and alighted on the ground near the carcass. The young birds advanced at once and began tearing at the flesh; while the two old birds stayed where they had alighted, as if disinclined to feed on half-putrid meat. Presently one of them sprang into the air and made a dash at the birds in the water, and instantly all the birds in the place rose into the air screaming loudly, the two young brown Caranchos only remaining on the ground. For a few moments I was in ignorance of the meaning of all this turmoil, when, suddenly, out of the confused black and white cloud of birds the Egret appeared, mounting vertically upwards with vigorous measured strokes. A moment later, and first one, then the other, Carancho also emerged from the cloud, evidently pursuing the Egret, and only then the two brown birds sprang into the air and joined in the chase. For some minutes I watched the four birds toiling upwards with a wild zigzag flight, while the Egret, still rising vertically, seemed to leave them hopelessly far behind. But before long they reached and passed it, and each bird as he did so would turn and rush downwards, striking at the Egret with his claws, and while one descended the others were rising, bird following bird with the greatest regularity. In this way they continued toiling upwards until the egret appeared a mere white speck in the sky, about which the four hateful black spots were still revolving. I had watched them from the first with the greatest excitement, and now began to fear that they would pass from sight and leave me in ignorance of the result; but at length they began to descend, and then it looked as if the Egret had lost all hope, for it was dropping very rapidly, while the four birds were all close to it striking at it every three or four seconds. The descent for the last half of the distance was exceedingly rapid, and the birds would have come down almost at the very spot they started from, which was about forty yards from where I stood, but the Egret was driven aside, and sloping rapidly down struck the earth at a distance of two hundred and fifty yards from the starting point. Scarcely had it touched the ground before the hungry quartette were tearing it with their beaks. They were all equally hungry no doubt, and perhaps the old birds were even hungrier than their young; and I am quite sure that if the flesh of the dead horse had not been so far advanced towards putrefaction they would not have attempted the conquest of the Egret. I have so frequently seen a pure white bird singled out for attack in this way, that it has always been a great subject of wonder to me how the two common species of snow-white Herons in South America are able to maintain their existence; for their whiteness exceeds that of other white waterfowl, while, compared with Swans, Storks, and the Wood-ibis, they are small and feeble. I am sure that if these four Caranchos had attacked a Glossy Ibis they would have found it an easier

A

conquest; yet they singled out the egret, purely, I believe. on account of its shining white conspicuous plumage." In his introduction Dr. Sclater gives a résumé of the number of genera and species inhabiting the Argentine Republic, and shows that the avifauna of that portion of South America belongs to the Patagonian sub-region. little sketch-map would have been useful, to show the configuration of the country and the proportions of the mountain-ranges, as it is evident that a district which can boast of a Dipper, and be at the same time the home of two Cariamas, must possess elements of two very differen! avifauna. Some day, no doubt, an exact exploration, such as that now being undertaken in Mexico by Messrs. Salvin and Godman, will trace the limits of the avifauna of the Pampas and the mountain regions. If Mr. Hudson could only be induced to resume his work of exploration and visit the interior of the Argentine Republic, the results would be, we venture to say, of the first importance to science.

Dr. Sclater, we notice, draws his comparisons of the different orders of Argentine birds from the "Nomenclator Avium Neotropicalium" of 1873, which is rather ancient history. The statistics of American birds must have altered considerably since that date, if we may judge from the Tanagers alone, which numbered 302 species in 1873, and in 1886 had reached 377 in number, according to Dr. Sclater's own estimate. In dividing the Neotropical Region into the sub-regions he adopts the conclusions of Prof. Newton in the "Encyclopædia Britannica," but the names of one or two of them are changed. The boundaries seem to be extremely natural, according to our present state of knowledge, though we would scarcely consider the Central American sub-region (or the Transpanamic sub-region, as Dr. Sclater renames it) to be bounded on the north by Tehuantepec! The author probably intended to give only a general outline, for the northern boundaries of the Central American sub-region are much more elaborately defined in fact.

R. BOWDLER SHARPE

OUR BOOK SHELF.

The Chemistry of the Coal-tar Colours. From the Ger man of Dr. R. Benedikt. Translated, with Additions, by Dr. E. Knecht. Second Edition. (London: George Bell and Sons, 1889.)

DR. BENEDIKT'S little book is a standard treatise in Germany, where the literature of the coal-tar colours is fast becoming a most important branch of the general literature of applied chemistry; and Dr. Knecht has done excellent service in making the work more generally known to English readers by means of his transla tion. It is remarkable that, although England may be said to have originated the coal-tar colour industry, she has contributed comparatively little to the general literature of the subject. Practically, all the systematized information we possess has come to us through the medium of French and German manuals. A number of our chemists could be named who have communicated original memoirs on the constitution of organic colouringmatters to the recognized organs of chemical research, but their work is very special in its character, and appeals rather to the pure chemist than to the technologist. and hence is seldom read by the latter. The want of a good, sound, and comprehensive treatise on the subject

of the coal-tar colour industry has, we think, not been without its influence on the development of this branch of applied organic chemistry in this country. Dr. Knecht's translation merits a place on the bookshelf of every person engaged in the manufacture and use of the so-called coal-tar colours.

A Bibliography of Geodesy. By J. Howard Gore, B.S., Ph.D. (Washington: Government Printing Office, 1889.)

THIS valuable work forms Appendix No. 16 to the 1887 Report of the United States Coast and Geodetic Survey, and is another example of the disinterested energy displayed by our Transatlantic cousins in scientific matters. With great perseverance, and at the cost of much time and trouble, Mr. Gore personally explored thirty-four of the principal libraries of Âmerica and Europe, and numerous minor libraries by proxy; and, in addition, he checked and completed many of his references by correspondence with the living authors of both continents. The extent of his labours is shown by the four hundred columns of references, and short remarks where the title alone is not sufficiently explanatory. An alphabetical arrangement is adopted, and this includes authors, abbreviations, and subjects.

It is gratifying to note that our own country, besides the assistance rendered by its libraries, lends its aid to such an important work in the shape of a manuscript supplement by Colonel Herschel to his pendulum bibliography, which was placed unreservedly at Mr. Gore's disposal, through the courtesy of the Royal Society. After the offers of publication made by various institutions, including the International Geodetic Association at Berlin, no further testimony to Mr. Gore's fitness for the work is needed, and the compiler is justly proud "to see the results of his labours issuing from an institution of his own country, which throughout the world is the recognized advance guard in geodetic science."

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 intended for this or any other part of NATURE, No notice is taken of anonymous communications.]

The Method of Quarter Squares.

I OMITTED any reference to Leslie in my review of Mr. Blater's table (NATURE, vol. xl. p. 573), as I have never supposed that he was an independent discoverer of the method, or an independent calculator of a table, of quarter squares. I have eferred to his table in my Report on Mathematical Tables Brit. Assoc. Report, 1873, p. 23); and the passage quoted by Prof. Carey Foster (p. 593) is given in full in the preface to Mr. Blater's table. It seems to me that the words in question**This application of a table of quarter squares, as it is derived from the simplest principles, might have readily occurred to a mathematician; yet I have nowhere seen it brought into practical use till, last summer, I met with, at Paris, a small book by Antoine Voisin, printed in 1817"-do not indicate an independent discovery; and this view is confirmed by the fact that, in the first edition of the "Philosophy of Arithmetic " (1817), Leslie makes no mention of quarter squares. It was only in the second edition (1820), after having seen Voisin's work in the previous year, that he added, at the end of the volume, an account of the method, and a table extending to 2000. The table was copied, I presume, from Voisin, as Leslie does not claim it as the result of his own calculation. In the British Association Report I have described it as "reprinted from Voisin," and have pointed out that it did not appear in the first edition. In the preface to Mr. Blater's letter it is described as "an extract from Voisin's table," Although we may, I think, infer, almost

with certainty, that the table is only a reprint,1 it is to be regretted that Leslie did not say so explicitly. J. W. L. GLAISHER. Trinity College, Cambridge, October 26.

Darwinism.

MR. ROMANES states that it is "absurd" to call his essay on physiological selection an elaborate (I said "laborious") attack upon Mr. Darwin's theory of the origin of species. In that essay I find these words (p. 345), "the theory of natural selection has been misnamed: it is not strictly speaking a theory of the origin of species"; and on p, 403, "the theory of physiological selection [.e. Dr. Romanes's theory] has this advantage over every other theory that has ever been propounded on the origin of species"; and again, "the problem of the origin of species which, as shown in the preceding paper [viz. the laborious essay?, his [Mr. Darwin's] theory of natural selection serves only in small part to explain."

On the other hand, Mr. Darwin entitled his great work, "The Origin of Species by means of Natural Selection, or the preservation of favoured races in the struggle for life." He considered his theory of natural selection to be a theory of the origin of species. Mr. Romanes says it is not. I say that this is an attack on Mr. Darwin's theory, and abcut as simple and direct an attack as possible. Why Mr. Romanes wishes us to believe that he did not attack Mr. Darwin's theory it is difficult to conceive. That he should hope to persuade anyone that it is absurd to call his essay an attack on Mr. Darwin's theory when this is what it

distinctly professes to be is curious. I trust you will not permit

an empty discussion on this matter, but leave it to your readers to find out by reference to the Proc. Linn. Soc., vol. xix., where the absurdity exists. E. RAY LANKESTER.

42 Half-moon Street, November 1.

Record of British Earthquakes.

WILL you allow me to ask your readers to help me in compiling notes of the earthquakes felt in this country during the present and following years?

Mr. Mallet's great Catalogue of all recorded earthquakes ends, as is well known, with the year 1842. Previously to this, Mr. David Milne had published a series of papers on the earthquakes of Great Britain in the Edinburgh New Philosophical Journal (vols. xxxi. to xxxvi. for the years 1841-44). These papers, which are of very great value, bring down our record to the end of August 1843. In recent years we have had the Catalogues of Prof. J. P. O'Reilly (Trans. Roy. Irish Acad., vol. xxviii. PP. 285-316 and 489-708) and the late Mr. W. Roper (published chronological list of shocks felt during the Christian era, down by T. Bell, Observer Office, Lancaster). The latter is a useful

to February 10, 1889; but, except in a few cases, it is little more than a list. Prof. O'Reilly's important catalogues are arranged alphabetically according to the localities affected, and do not pretend to give detailed information with reference to the shocks themselves.

To make our seismic record more complete, I propose, therefore, to compile a descriptive list of British shocks noticed in newspapers and scientific journals from the time at which Mr. Milne's Catalogue closes down to the end of the year 1888; and I should be very grateful if your readers can in any way help me in this work.

What I wish particularly to ask for, however, is information relating to the shocks of the present and future years. For our knowledge of British earthquakes we must at present rely to a great extent on newspaper accounts; and these accounts, which for some points are fairly trustworthy, become difficult of access in after years. If any of your readers are willing to assist me in preserving these notices in a convenient and systematic form, may I ask if they would be good enough to send, to the address below, the names and dates of newspapers, and more especially local ones, in which any descriptions, however short, are given of British shocks? It is hardly necessary to say that any other notes, communicated by those who have felt the shocks or observed their effects, would be of great value, and would be most thankfully received.

The days are past for compiling earthquake catalogues for the After quoting the full title of Voisin's table, Leslie refers to his own table as "the specimen which I have given."

whole surface of the earth, and the value of an attemp` at such a task would now be extremely doubtful. But for limited districts, like this country, the case is very different. It would indeed be difficult to over-estimate the value of a seismic record which can claim any approach to completeness for a definite earthquake area, however feeble the shocks which visit it may be. I may add that I hope shortly to publish some notes or directions for the study of earthquakes, with special reference to those which occur in this country. CHARLES DAVISON.

38 Charlotte Road, Birmingham, October 10.

Effects of Lightning.

I HAVE known of the following case since July last, but owing to absence from this place have only been able to get particulars during the last few days.

66

During the terrific storm of the 12th of July last, a labourer's cottage was struck by lightning at Leagrave, near here. The lightning descended, according to an eye-witness's report, like a 'spout of fire," and struck and descended the chimney, which it destroyed. In the room below there was an old shepherd, an invalid woman, a child, and a shepherd's dog. The shepherd was sitting in a chair leaning on a stick, a kettle was boiling on the fire, and the door was open. The lightning entered the room simultaneously by the chimney and an adjoining window. The window was utterly destroyed, and the kettle was thrown from the fire across the room, the stick on which the shepherd was leaning was torn from his hand and also thrown across the room, the lightning entered a cupboard containing glass and crockery and destroyed every article, and plaster was torn from the walls. The man and woman remained unhurt, but the child was thrown down and its knees stiffened. The dog was struck perfectly stiff, "like a log of wood," and was considered dead. The room seemed full of fire, water, and sulphur, and the occupants said the smell of sulphur was so strong that they would certainly have been suffocated had it not been for the open door. After the storm had abated, the dog, with all its limbs stiff, was laid in a barn, where it very slowly and partially recovered. It long remained both deaf and blind, and was entirely dependent upon smell for its recognition of persons and things. To the present day it has not entirely recovered its injured senses. Dunstable.

Electrical Cloud Phenomenon.

W. G. S.

A SHORT description of a curious cloud appearance observed by me this summer may be of interest to your readers. It was noticed in Kiushu, the southernmost of the three great islands of Japan, early in July, at a distance of ten or twelve miles from the sea.

The season had been, and was, after the time of the observation, an exceptionally rainy one, severe floods being produced in almost all parts of the country, but it was not raining in the place where I made the observation at that particular time. Time shortly after midday, thermometer about 85° F.

The sky was clear overhead, but there was a great bank of heavy "thunderous" looking clouds to the south. It is most difficult to judge even approximately of the distance of clouds, but these might be from one to two miles off; the lower edge was represented by a very nearly straight line, and there was an amount of blue sky visible under the clouds that would perhaps subtend from Ic° to 15°.

My attention was attracted to a sort of "tail" of cloud stretching itself downwards from the straight under side of the cloud-bank. It gradually extended till it reached some twothirds of the distance from the cloud to the earth. It remained of about constant length for a little over ten minutes, the lower end continually waving about in a most curious way, giving the impression almost that it was feeling for something.

Quite suddenly the filament of cloud straightened itself out, and extended itself towards the earth. The lower end became so very thin that, from the distance, it was impossible to see whether it actually made contact with the earth or not, but I have not the smallest doubt that it did, and that a silent discharge took place at the time. There was certainly no sound heard. Immediately after the contact the filament rapidly drew itself up to the cloud, and was incorporated with it. Almost immediately after this, whether as a mere coincidence or not I cannot tell, the cloud discharged a great amount of rain. W. K. BURTON.

Imperial University, Tokio, Japan.

P.S.-The appearance was not unlike the illustrations of "water-spouts that I have seen, but there was no whirling motion such as is always described as accompanying these, nor, indeed, was there any evidence of violent disturbance of any kind at all.

The Use of the Word Antiparallel.

THE following note on the use of the word antiparallel may prove of interest to the readers of NATURE.

In the second edition of "A New Mathematical Dictionary" by E. Stone, F.R.S. (London, 1743), appears a short article on antiparallels, the whole of which I will quote:

Antiparallels, are those lines, as FE, BC, that make the same angles AFE, ACB, with the two lines AB, AC, cutting them, but contrary ways, as parallel lines that cut them. But Mr. Leibnitz, in the Acta Erudit., An. 1691, p. 279, calls antiparallels those lines (see Fig. 2) as EF, GH, which cut two parallels AB, CD; so that the outward angle AIF, together with the inward one AKH, is equal to a right angle. When

the sides AB, AC, of a triangle, as ABC (Fig. 1), are cut by a line EF antiparallel to the bis: BC, the said sides are cut reciprocally proportional by the said line EF; that is, AF: BF:: EC: AE, the triangles AFE, ABC being similar or equiangular.'

The error in regard to the ratios of the segments of the sides is the same as the one noted in Hatton's Miscellanea Mathematica," as quoted by Mr. Langley. I have no doubt that earlier instances of the use of this word can be found, and I would like to know whether the word is used in the first edition of "Stone's Dictionary." W. J. JAMES.

Wesleyan University, Middletown,
Conn. U.S.A., October 15.

Fossil Rhizocarps.

IN Bennet and Murray's "Cryptogamic Botany," at p. 115, I am surprised to find in a reference to my paper on Fossil Rhizocarps" (in Bull. Ac. Sciences, Chicago) the statement, with reference to the macrospores of Protosalvinia, that "inasmuch as they are borne on Lepidoden Iron scales this reference is inadmissible." Now no such fact has come to my knowledge, and on the contrary these bodies are found inclosed in cellular sporocarps like those of Salvinia, and are so described in the paper in question. If anyone has found them on "scales of Lepidodendron," the authority should have been stated. Montreal, October 15. J. WM. DAWSON.

Specific Inductive Capacity.

ON p. 669 of Ganot's "Physics" (eleventh edition) the following statement is found:"At a fixed distance above a gold-leaf electroscope, let an electrified sphere be placed, by which a certain divergence of the leaves is produced. If now, the charges remaining the same, a disk of sulphur or of shellac be interposed, the divergence increases, showing that inductive action takes place through the sulphur to a greater extent than through a layer of air of the same thickness.'

If this statement were correct, there should be less electric action on the side of the ball furthest from the electroscope when the dielectric is interposed. To test this I arranged an experiment as follows:

The knob of a charged Leyden jar was placed midway between two insulated plates of metal, each plate being in connection with an electroscope. The leaves of each electroscope now diverged to an equal extent.

A plate of ebonite was now placed between the knob of the jar and one of the plates. If the statement above quoted is

correct, the leaves of the electroscope in connection with this plate should show an increased divergence, but the reverse effect was observed. The leaves partially collapsed. In all experi men's that I have made by inserting dielectrics between a charged body and an electroscope, less electric action has been the result. If while the charged ball be near the electroscope the plate of it be touched with the finger, the leaves collapse, and on removing the finger and then the charged ball they again diverge.

Now let a dielectric be placed between the ball and the electroscope, touch the latter, and remove the finger and ball as before, and much greater divergence will be produced. In both cases the electroscope is charged by induction. Without putting the electroscope to earth, I fail to see theoretically why any greater divergence should occur. I suppose someone must have made the experiment as quoted, but if a greater effect was produced it must have been caused by the substance used for a dielectric being charged itself. I have found very great difficulty in preventing plates of ebonite, paraffin, sulphur, &c., becoming electrified when placed near a charged body.

I should like to know if anyone has experimented in this direction, because either the text-books or myself must be wrong. In Guthrie's book (p. 101) there is a statement similar to Ganot's. W. A. RUDGE.

Who discovered the Teeth in Ornithorhynchus ? Ox returning from Central Arizona, where I have been engaged in biological explorations, I find upon my desk an important paper entitled "On the Dentition of Ornithorhynchus," by my friend Mr. Oldfield Thomas, Curator of Mammals in the British Museum (see Proc. Royal Soc., vol. xlvi, 1889, 126–131, pl. 2).

that the details of the process, which is practised daily in thousands of workshops, are so well known that it is unnecessary to devote a lecture to the subject. It seemed to me that the entire question was the most important I could choose, partly because it will enable a large number of people who are engaged in industrial work, and who are not expected to think about it in a scientific way, to know how such facts as we shall have to examine have been dealt with by scientific investigators; while those of our members who do not consider that their thoughts or work are scientific in its strictest sense, may perhaps be interested to see how absolutely industrial progress depends upon the advancement of science. This consideration has led me to deal with the subject in a somewhat comprehensive way. The treatment of iron in its several forms is the thing that we as a nation do well. If it be true that national virtues are manifestly expressed in the industrial art of a people, we may recall the sentence in Mr. Ruskin's "Crown of Wild Olive" in which he says, "You have at present in England only one art of any consequence-that is, iron-working," adding, with reference to the manufacture of armour-plate, "Do you think, on those iron plates your courage and endurance are not written for ever, not merely with an iron pen, but on iron parchment?" It may be well, therefore, to consider what properties iron possesses which entitle its application to industrial use to specially represent the skill and patience of the nation.

In 1863, Lord Armstrong, in his address as President of this Association, expressed the hope "that when the time again comes round to receive the British Association in this town, its members will find the interval to have been as fruitful as the corresponding period," since the previous meeting in 1838, "on which they were then

From the above I infer that considerable stir has been made

by the assumed new "discovery" that the young Ornithorhynchus

has teeth.

If my British colleagues will turn to the masterly work of their illustrious countryman, Sir Everard Home, they will find in the second volume of his "I ectures on Comparative Anatomy" (published in 1814), no less than three beautifully engraved plates, containing eight figures, of the skull and mouth parts of Ornithorhynchus. Four of these figures show the teeth -two on each side of each jaw. The explanation accompanying Fig. 1, Tab. lix., is as follows: "A view of the upper jaw and palate, to show that there are two grinding teeth on each side." Fig. 2 is "a similar view of the under jaw,' Washington, D.C., October 12. C. HART MERRIAM.

realized, for the efforts of the last twenty years have resulted in the development of an "age of steel." When material, although Bessemer had, seven years before, the Association last met here, steel was still an expensive communicated his great invention to the world through the British Association at its Cheltenham meeting. The great future in store for Siemens's regenerative furnace, which plays so important a part in the manufacture of steel, was confidently predicted in his Presidential address by Lord Armstrong, than whom no one was better able to judge, for no one had done more to develop the use of

steel of all kinds.

Steel, we shall see, is modified iron. The name iron is in fact a comprehensive one, for the mechanical behaviour of the metal is so singularly changed by influences acting from within and without its mass, as to lead many to think, with Paracelsus, that iron and steel must be two

STEEL I.

HE fact that the British Association meets this year THE at Newcastle no doubt suggested to the Council that it would be well to provide, for the first time since 1848, a lecture on a metallurgical subject. In that year a discourse was delivered at Swansea by Dr. Percy, one of the most learned metallurgists of our time, who has recently passed away, after having almost created an English literature of metallurgy by the publication of his well-known treatises, without which it would have been comparatively barren. It was to him that the country turned in 1851 when it became evident that our metallurgists must receive scientific training.

I know that it has occurred to many that the various problems involved in the "hardening and tempering of steel" must be incapable of adequate treatment in the brief limits of a discourse like this, while others will think

A Lecture delivered on September 13, by Prof. W. C. Roberts-Austen, F.R.S., before the members of the British Association.

iron may be prepared in a form as pliable and soft as copper, steel can readily be made sufficiently hard to cut glass, physical properties of iron and certain kinds of steel, the and notwithstanding this extraordinary variance in the chemical difference between them is comparatively very small, and would hardly secure attention if it were not for the importance of the results to which it gives rise. We have to consider the nature of the transformations which iron can sustain, and to see how it differs from steel, of which an old writer has said, "Its most useful and advantageous property is that of becoming extremely hard produced being greater in proportion as the steel is hotter when ignited and plunged into cold water, the hardness and the water colder. The colours which appear on the surface of steel slowly heated direct the artist in tempering or reducing the hardness of steel to any determinate

standard." There is still so much confusion between the words "temper," "tempering," and "hardening," in the writings of even very eminent authorities, that it is well

1790).

"The First Principles of Chemistry," by W. Nicholson, p. 312 (London,

to keep these old definitions carefully in mind. I shall employ the word tempering in the sense of softening, as Falstaff uses it when he says of Shallow :

"I have him already tempering between my finger and my thumb, and shortly will I seal with him." 1

softening, that is, as brittle wax does by the application of gentle heat. Hardening, then, is the result of rapidly cooling a strongly heated mass of steel. Tempering consists in re-heating the hardened steel to a temperature far short of that to which it was raised before hardening: this heating may or may not be followed by rapid cooling. Annealing consists in heating the mass to a temperature higher than that used for tempering, and allowing it to cool slowly.

First, let the prominent facts be demonstrated experimentally.

[Three sword-blades of identical quality, made by an eminent sword-smith, Mr. Wilkinson, were taken. It was shown by bending one that it was soft; this was heated to redness and plunged into cold water, when it became so hard that it broke on the attempt to bend it. Another was bent into a bow, the arc of which was four inches shorter than the sword itself, a common test for "temper," and it sprang back to a straight line when the bending force was removed; this had been tempered. A third, which had been softened by being cooled slowly, bent easily and remained distorted ]

The metal has been singularly altered in its properties by comparatively simple treatment, and all these changes it must be remembered have been produced in a solid metal to which nothing has been added, and from which nothing material has been taken. The theory of this operation which I have just conducted has been laboriously built up, and its consideration introduces many questions of great interest both in the history of science, and in our knowledge of molecular physics. First as regards the history of the subject. The knowledge that steel might be hardened must have come to us from remote antiquity. Copper hardened with tin was its only predecessor, and it continued to be used very long after it was known that steel might be hardened. It would, moreover, appear that a desire to appreciate the difficulties of a people to whom cutting instruments of hard steel were unknown, seems to have induced experimenters in quite recent times to fashion implements of bronze, and a trustworthy authority tells us that "Sir Francis Chantry formed an alloy containing about 16 parts of copper, 2 of zinc, and 2 of tin, of which he had a razor made, and I believe even shaved with it.' The Greek alchemical manuscripts which have been so carefully examined by M. Berthelot give various receipts from which it is evident that in the early days the nature of the quenching fluid was considered to be all-important. There were certain rivers the waters of which were supposed to be specially efficacious. Pliny, who says that the difference between waters of various rivers can be recognized by workers in steel, also knew that oil might be used with advantage for hardening certain varieties of the metal. It is sad to think how many of the old receipts for hardening and tempering have been lost. What would we not give, for instance, for the records of the Gallic prototype of our Iron and Steel Institute, the "Collegium Fabrorum Ferrariorum,"3 a guild with similar aims, formed in the time of the Roman Republic, for the advancement of knowledge, for the good of the State, and not for that of its individual members? The belief, however, in the efficacy of curious nostrums and solutions for hardening steel could hardly have been firmer at any period than in the sixteenth century of our era.

1 King Henry IV, Part II., Act iv., Scene 3.
2" Engines of War," by H. Wilkinson, p. 194 (1841).

3 "La Ferronnerie," par F. Liger, t. ii. p. 147 (Paris, 1875).

Shake

speare suggests that thello's sword "of Spain" had been hardened in a cold stream for he says it had

"the ice brook's temper ";

but cold water was far too simple a material for many a sixteenth century artificer to employ, as is shown by the quaint recipes contained in one of the earliest books of trade secrets, which, by its title, showed the existence of the belief that the "right use of alchemy" was to bring chemical knowledge to bear upon industry. The earliest edition was published in 1531, and the first English translation in 1583, from which the following extracts may be of interest. Take snayles, and first drawne water of a red die of which water being taken in the two firste moneths of haruest when it raynes," boil it with the snails," then heate your iron red hote and quench it therein and it shall be hard as steele." "Ye may do the like with the blood of a man of xxx yeres of age, and of sanguine complexion, being of a merry nature and pleasaunt . distilled in the middst of May." This may seem trivial enough, but the belief in the efficacy of such solutions survived into the present century, for I find in a work published in 1810 that the artist is prettily directed to take the root of blue lilies, infuse it in wine and quench the steel in it," and the steel will be hard; on the other hand, he is told that if he "takes the juice or water of common beans and quenches iron or steel in it, it will be soft as lead." I am at a loss to explain the confusion which has arisen from this source. As must always be the case when the practice of an art is purely empirical, such procedure was often fantastic, but it is by no means obsolete, for probably at the present day there is hardly a workshop in which some artificer could not be found with a claim to possess a quaint nostrum for hardening steel. Even the use of absurdly compounded baths, to which I have referred, was supported by theoretical views. Otto Tachen, for instance, writing of steel in about the year 1666, says that steel when it is "quenched in water acquires strength because the light alcaly in the water is a true comforter of the light acid in the iron, and cutlers do strengthen it with the alcaly of animals," hence the use of snails. Again, Lemery explains in much the same way the production of steel by heating iron in the presence of horns of animals.

5

I have dwelt so long on these points in order to bring out clearly the fact that the early workers attached great importance to the nature of the fluid in which hot steel was quenched, and they were right, though their theories may have been wrong. The degree of rapidity with which heat is abstracted from the steel during the operation of hardening is as important at the present day as it ever was. Roughly speaking, if steel has to be made glass-hard, ice-cold water, brine, or mercury, is used; if it has only to be made slightly hard, hot water or oil may be employed; while, as Thomas Gill suggested in 1818, both "hardening" and "tempering " may be united in a single operation by plunging the hot metal in a bath of molten lead or other suitable metal, which will of course abstract the heat more slowly.

We must now trace the development of theories relating to the internal constitution of steel. The advent of the phlogistic school with the teaching of Becher and Stahl led to the view that iron gained phlogiston during its conversion into steel. By phlogiston we know that the early chemists really meant energy, but to them phlogiston was represented to be a kind of soul possessed by all metals,

"Rechter Gebrauch d. Alchimei," 1531. There were many English

editions.

"A profitable boke declaring dyuers approoned remedies," &c. (London, 1583). See Prof. Fergus n's learned paper "On some Early Treatises on Technological Chemistry," Phil. Soc., Glasgow, January 1826. 3" The Laboratory or School of Arts," 6th edition, 1799. p. 228. There is a later edition of 1810.

4"His Key to the Ancient Hippocratical Learning," p. 68 (London, 1690).

5A Course of Chemistry," and edition, 1686, p. 131.

6 Thomson's Annals of Philo ophy, xii., 1818, p. 58.