Miscellanies, 189 



Prinsep, that lead and sulphur combined, in varying proportions, 

 fi-oni yi^f to yV of sulphur, did not prevent the formation of bubbles ; 

 but when the sulphur was increased to |, no more bubbles appeared ; 

 upon critical investigation he ascertained that the proportion of sul- 

 phur to the lead, at which the action ceased, was precisely that of 

 'Common sulphuret of lead ; and the same experiments having given 

 the same result, with respect to the sulphuret of tin, he inferred that 

 the proper combination, in determinate proportions, is necessary to 

 prevent the metals in contact from producing electricity, and that the 

 influence of the mere mixture was nothing. This result he deems 

 of some consequence to the mineralogist. — Bib. Univ. Fev. 1830. 



11. Daily Magnetic T^ariation. — According to experiments made 

 by Humboldt, it appears that the daily variation is by no means the 

 same in different places. On the 29th of January, the variation at 

 Berlin was three times greater than on the 27th; whereas, at Paris, 

 on the 29th. it was much less than that of the 27th. at Berlin. At 

 Berlin, the variation, on the 11th. of January, was tvv^ice that of the 

 10th. at Paris; that of the 10th. was greater than that of tlie 11th. 



These results do not appear to depend on any error of observa- 

 tion, but are real consequences of local causes. By trials made at the 

 mouth and lowest part of the Freyberg mines, it was found that at a 

 depth of seven hundred and ninety eight feet in the earth had no 

 sensible influence upon the inclination of the needle. — Quarterly 

 Journal of Science. 



12. Economical process for Imitating Silver paper. — The follow- 

 ing Chinese method has been made known in Europe by Pere du 

 Halde : — Take two scruples of gelatine, or Flanders' glue, made of 

 ox-hide, one scruple of alum, a pint of water. Place the whole over 

 a slow fire until the water is almost wholly evaporated. Spread 

 some sheets of paper upon a table, and with a brush lay on two or 

 three coats of this glue ; then take powder made of a certain quan- 

 tity of talc boiled, and one third of the same quantity of alum. Af- 

 ter having well pounded these substances, sift them, then boil them 

 again in water, then dry them in the sun, and pound them again. 

 The powder, which is then very fine, is to be passed through a very 

 fine sieve upon the sheets of prepared paper. The talc powder is 

 glued fast : it is dien to be dried in the shade ; after which remove 

 the superfluous powder with a piece of cotton. — Jour, des Connoiss. 

 Usuelles. 



