470 InteUigence and Miscellaneous Articles. 



Note. In fact, from the preceding Table it follows that the core 

 and the tube are magnetized in the same direction before the cooling 

 of the system, that the initial magnetization M' of the tube sur- 

 passes that of the core while the current is feeble, but that ibhe 

 magnetization M of the core excels that of the tube when the in- 

 tensity of the current passes a certain limit. Accordingly it is the 

 magnetism of the core that will be reversed during the cooling, in 

 the case of feeble currents, and, on the contrary, the magnetism of 

 the tube that has to undergo reversal in the case of more energetic 

 currents. 



In regard to the different quantitative ratios which establish 

 themselves between the two magnetisms M and M', according as 

 the current is more or less intense, they are easily accounted for 

 hy starting from the principle laid down by M. Jamin, that the 

 current penetrates to a greater depth the more energetic it is. 



The experiments performed upon the tubes of |, j, and 1 millim. 

 thickness gave results entirely analogous to those which I have 

 here described. — ComjJtes Rendus de VAcademie des Sciences^ Oct. 1, 

 1877, tome Ixxxv. pp. 615-617. 



ON THE DISAGGREGATION OF TIN. 



The observation has been made before, that organ-pipes after 

 long use become brittle and fall to pieces. In a similar manner, 

 as stated by Oudemans *, plates of pure tin, containing at the most 

 only 0-3 per cent, of lead and iron, have, during conveyance by 

 railway from Rotterdam to Moscow in severe cold, broken into 

 small fragments resembling sulphide of molybdenum. 



According to a trustworthy communication from the Eoyal Pyro- 

 technic Laboratory at Spandau, a similar phenomenon has been 

 recently observed. A large quantity (295 kilograms) of tin-plate 

 acquired laminar exfoliations, in which it crumbled into minute 

 particles. Similarly, but in a less degree, larger quantities (1950 

 kilograms) of blocks of tin subsequently suffered. The warehouses 

 were thoroughly dry ; the tin contained merely traces of foreign 

 metals, no sulphur or phosphorus, and no oxide of tin. According 

 to the account of Dr. Petri, the tin could be more easily pulverized 

 than filings of unaltered tin, and evolved hydrogen more quickly 

 with acid. Within the time during which it lay in the warehouse 

 there was no severe winter; and, moreover, the disaggregation 

 continued. 



Prom all these observations it appears probable that in this dis- 

 aggregation the repeated little shocks, combined with frequent 

 strong variations of temperature (for example, considerable refri- 

 gerations), essentially cooperated. — Poggeudorft"s Annalen, 1877, 

 ISo. 10 ; new series, vol. ii. p. 304. 



* Chnn Jahrcfih. 1872, p. •2'5Q. 



