Feb. 6, 1890] 



NATURE 



333 



lo the Royal Society.^ As already stated, this material contains 

 25 per cent, of nickel and about 74 per cent, of iron, and over 

 a range of temperature from something below freezing to 580° C. 

 it can exist in two states, magnetic and non-magnetic. 



The wire as sent to me was magnetizable as tested by means 

 of a magnet in the ordinary way. On heating it to a dull red- 

 ness, it became non-magnetizable, whether it was cooled slowly 

 or exceedingly rapidly by plunging it into water. A quantity 

 of the wire was brought into the non-magnetizable state by 

 heating it, and allowing it to cool. The electric resistance of a 

 portion of this wire, about 5 metres in length, was ascertained 

 in terms of the temperature ; it was first of all tried at the 

 ordinary temperature, and at temperatures up to 340° C. The 

 specific resistances at these temperatures are indicated in the 

 curve by the numbers i, 2, 3. The wire was then cooled by 

 means of solid carbonic acid ; the supposed course of change of 

 resistance is indicated by the dotted line on the curve ; the actual 

 observations of resistance, however, are indicated by the crosses 

 in the neighbourhood of the letter A on the curve. The wire 



was then allowed to return to the temperature of the room, and 

 was subsequently heated, the actual observations being showi> 

 by crosses on the lower branch of the curve ; the heating was- 

 continued to a temperature of 680' C, and the metal was then 

 allowed to cool, the actual observations being still shown by 

 crosses. From this curve, it will be seen that in the two states 

 of the metal, magnetizable and non-magnetizable, the resist- 

 ances at ordinary temperatures are quite different. The specific 

 resistance in the magnetizable condition is about o'oooofa, in 

 the non-magnetizable condition it is about 0"000072. The curve 

 of resistance in terms of the temperature of the material in the 

 magnetizable condition has a close resemblance to that of soft 

 iron, excepting that the coefficient of variation is much smaller, 

 as, indeed, one would expect it to be in the case of an alloy ;. 

 at 20° C. the coefficient is about 0*00132, just below 600° C. it 

 is about 0'0040, and above 600° it has fallen to a value less than 

 that which it had at 20° C. The change in electrical resistance 

 effected by cooling is almost as remarkable as the change in the 

 magnetic properties. 



- eoo - 100 



zoo" 300° 400 



SOO' 700° 800' C 



Samples of the wire were next tested in Prof. Kennedy's 

 laboratory for mechanical strength. Five samples of the wire 

 were taken which had been heated and were in the non-mag- 

 netizable state, and five which had been cooled and were in the 

 magnetizable state. There was a marked difTerence in the 

 hardness of these two samples ; the non-magnetizable was ex- 

 tremely soft, and the magnetizable tolerably hard. Of the five non- 

 magnetizable samples the highest breaking stress was 50*52 tons 

 per square inch, the lowest 4875 ; the greatest extension was 33*3 

 per cent., the lowest 30 per cent. Of the magnetizable samples, 

 the highest breaking stress was 88 '12 tons per square inch, the 

 lowest was 8576; the highest extension was 8-33, the lowest 

 670. The broken fragments, both of the wire which had 

 originally been magnetizable and that which had been non- 

 magnetizable, were now found to be magnetizable. If this 

 material could be produced at a lower cost, these facts would 

 have a very important bearing. As a mild steel the non-mag- 

 netizable material is very fine, having so high a breaking stress 

 for so great an elongation at rupture. Suppose it were used for 

 any purpose for which a mild steel is suitable on account of this 

 considerable elongation at rupture, if exposed to a sharp frost 

 its properties would be completely changed — it would become 

 essentially a hard steel, and it would remain a hard steel until 

 it had been heated to a temperature of about 600° C, 



Geological Society, January 22.— W. T, Blanford, F.R.S., 

 President, in the chair. — The following communication was 

 read :— On the crystalline schists and their relation to the Meso- 

 zoic rocks in the Lepontine Alps, by Prof. T. G. Bonney, 

 F.R. S. In the debate upon the paper on two traverses of the 

 crystalline rocks of the Alps (read December 5, 1888) it was 

 stated that rocks had been asserted on good authority to exist in 

 the Lepontine Alps, which contained Mesozoic fossils, together 

 with garnets, staurolites, &c., and thus were undistinguishable 

 from crystalline schists regarded by the author as belonging to 

 the presumably Archaean massifs of that mountain-chain. In 

 reply the author stated that he regarded this as a challenge to 

 demonstrate the soundness or unsoundness of the hypothesis to 

 which he had committed himself. The present paper gives the 

 result of his investigations, undertaken in the month of July 



' See Address to the Institution of Electrical Engineers (Nature, January 

 23. p. 274). 



1889, in company with Mr. James Eccles, to whom the author is 

 deeply indebted for invaluable help. The paper deals with the 

 following subjects : — (i) T/te Andermatt Section. By the geo- 

 logists aforepaid, a highly crystalline white marble which occurs- 

 on the northern side of the Urserenthal trough, at and above 

 Altkircb, near Andermatt, is referred to the Jurassic series 

 (members of w hich undoubtedly occur at no great distance, 

 almost on the same line of strike). The author describes the 

 relation of the marble to an adjacent black schistose slate, and 

 discusses the significance of some markings in the former which 

 might readily be considered as organic, but to which he assigns 

 a different origin. He shows that there are most serious 

 difficulties in regarding these two rocks as members of the same 

 series, and explains the apparent sequence as the result of a 

 sharp and probably broken infold, as in the case of the admitted 

 band of Carboniferous rock at Andermatt itself. That the sec- 

 tion is a difficult one on any hypothesis the author admits, but 

 in regard to the former of these, after a discussion of the 

 evidence, he concludes, " that tendered on the spot demands a 

 verdict of ' not proven ' — that obtainable in other parts of the 

 Alps, will compel us to add, 'not provable.' (2) The Schists 

 of the Val Piora. These schists, already noticed by the author 

 in his Presidential address to the Society in 1886, occur in force 

 near the Lago di Ritom, and consist of two groups — the one 

 dark mica-schists,s ometimes containing conspicuous black 

 garnets, banded with quartzites, the other various calc-mica 

 schists ; between them, apparently not very persistent, occurs 

 a schist containing rather large staurolites or kyanites. On 

 the north side is a prolongation of the garnet-actinolfte 

 (Tremola-) schists of the St. Gothard and then gneiss, 

 on the south side gneiss. There is also some rauchwacke. 

 This lock, at first sight, appears to underlie the Piora 

 schists, and thus to be the lowest member of a trough. If 

 so, as it is admittedly about Triassic in age, the Piora schists 

 would be Mesozoic. The author shows that (i) the latter rocks 

 do not form a simple fold ; (2) they are, beyond all question, 

 altered sediments ; (3) they have often been greatly crushed 

 subsequent to mineralization ; (4) the garnets, staurolites, 

 &c. (if not injured by subsequent crushing) are well de- 

 veloped and characteristic, and are authigenous minerals. 

 (3) The Ratichxvacki and its Relation to the Schist, {a) The Vat 

 Piora Sections : Th.t author shows that the rauchwacke, which 



