Foreiorn Literature and Science. 



183 



116 oscillations above a plate of marble. 

 112 over a stratum of mercury 2 lines 



thick. 



106 over a plate of Bismuth, 



94 - - Platina, - 



90 - - - Antimony, 



89 - - Lead, 



89 - - - Gold, - 



71 - - Zinc, - 



68 - - - Tin, - - 



62 - - Brass, 



62 - - - Copper, 



55 - - Silver, - 



6 - - - Iron, - ■ 

 The author ascertained by experiment, that the metallic 

 nature of the magnetic needle had the same influence on 

 the oscillations as subjacent plates, and that by combining 

 the metals, which, like iron, nickel and cobalt, are magnetic, 

 with others, which, like antimony, diminish the magnetic 

 force, — compounds are formed, which have no influence on 

 the oscillations of the magnetic needle. He thus found 

 that an alloy of 4 parts antimony with 1 of iron, of 3 cop- 

 per with I anitimony, and of 2 copper with 1 nickel, produ- 

 ced not the least dimunition in the number of oscillations 

 which were 1 16 as vi'hen over a plate of marble. He infers 

 from these facts that those three alloys, would be the most 

 suitable for compasses, and that that of copper and nickel 

 deserves the preference, from its being the most malleable. 

 — Ferrussac''s Bull. Aout, 1827. 



29. Artificial Spider'' s w eh for micrometers — Dissolve, to 

 a convenient extent very thin caoutchouc in very pure spirits 

 of turpentine. By drawing out the solution, extremely fine 

 and smooth threads are obtained, which when dried, are ve- 

 ry good for micrometers. — Ihid. 



30. Analysis of Potteries. — M. P. Berthier has examined 

 the composition of several kinds of pottery ware. He dis- 

 tinguishes them into three sorts — 1st, porcelains, 2d, potte- 

 ries, 3d, crucibles. 



