Intelligence and Miscellaneous Articles. 469 



in the gravels may be due to submergence of the plateau up to a 

 height of at least 400 feet above present sea-level, and cites other 

 facts in support of this suggestion. He concludes that the precise 

 age of the gravel can only be more or less of a guess, until the mode 

 of its formation has been definitely ascertained. 



3. "A Fossiliferous Pleistocene Deposit at Stone, on the Hamp- 

 shire Coast." By Clement Reid, Esq., E.L.S., E.G.S. 



This is practically a supplement to a paper, ' On the Pleistocene 

 Deposits of the Sussex Coast,' that appeared in the last volume of 

 the Quarterly Journal. An equivalent of the mud-deposit of Selsey 

 has now been discovered about 20 miles farther west, and from it 

 have been obtained elephant-remains, and some mollusca and plants 

 like those found at Selsey. Among the plants is a South European 

 maple. 



XLVII. Intelligence and Miscellaneous Articles. 



ON VILLARl'S CRITICAL POINT IN NICKEL. 

 BY PROF. HEYDWEILLER. 



rPHE magnetism of iron, nickel, and cobalt changes under the 

 ■*- influence of stretching forces. Villari first observed a special 

 behaviour of iron in reference to this attribute, namely that with 

 moderately strong magnetization small stretching forces increase 

 the magnetism, while larger forces diminish it; thus the strength 

 of the magnetism is graphically represented as a function of the 

 load, the ordinates of the curve first increase up to a maximum and 

 then diminish to far below the original values. The point of the 

 curve at which the ordinate again reaches the original value is 

 named Villari's critical point. 



In nickel this property has not been observed up to the present ; 

 in this case, so far as hitherto known, the magnetism steadily 

 decreases with increasing load. But with strongly magnetized 

 soft iron also, with small load, the original increase of the mag- 

 netism vanishes, and it was thought probable that with sufficiently 

 weak magnetization nickel also possesses a Villari's critical point. 

 Experiments have confirmed this expectation. In observing the 

 changes in the very feeble magnetizations, it was found necessary 

 to work with a very sensitive arrangement. 



A chemically pure nickel wire, 46 cm. long and 0*15 era. thick, 

 was suspended vertically with its lower end very near (3*5 cm. 

 distant) the upper magnetic needle of an astatic system, and so 

 that small longitudinal displacements caused no perceptible altera- 

 tion in the direction of the needle. An intensity of magnetization 

 1 = 1 C.Gr.S. unit corresponded to about 90 p throw with 110 p 

 scale distance. 



The reduction of the observed numbers to absolute measure was 

 effected by comparison with an auxiliary magnetometer with single 

 needle. 



Phil. Mag. S. 5. Vol. 35. No. 216. May 1893. 2 K 



