388 Foreign Literature and Science. 



Arcnilla. It is used in all Peru and especially in the prov- 

 ince of Arequipa and in Chili as sand in letter writing. The 

 muriate in these grains is mixed with quartz which is its 

 gangue. 



The nitrate of soda in the district of Atacamn is found in 

 beds of variable thickness, extending more than fifty leagues, 

 covered with clay. The quantity is so great that more than 

 40,000 quintals have already been obtained, and the propri- 

 etor will engage any portion that may be desired. The salt 

 in some places is extremely pure ; in others it is mixed 

 with clay, which is easily separated by solution and crystal- 

 lization 



33. Galvanic Instruments. — Electro Magnetism. — The 

 beautiful discovery of Oersted of the magnetic power of the 

 galvanic battery, has excited the zeal of philosophic experi- 

 menters alniost every where. A magnificent apparatus was 

 constructed last year at the Imperial Museum of Florence, 

 under the direction of Count Girolamo de Bardi, director of 

 that establishment ; and the experiments with it were per- 

 formed by himself, assisted by M. Gazzeri, professor of 

 chemistry in the hospital of S. Maria Nuova of that city, 

 and Car. Antiu'U'i, professor of a philosophical cabinet, to- 

 gether with Prof. Pictet, and Dr. Marcet, of Geneva, who 

 were then in Florence. 



This machine consisted of six plates of zinc each, with a 

 double surface of copper, and containing in the whole 4101G 

 square inches of active surface. The plates of copper were 

 put together so as to form cells or troughs, in e^ch of 

 which a zinc plate was immersed and kept insulated from 

 the copper by being previously put into a linen bag. Brass 

 conductors establish the communication between the zinc 

 of each trough and the copper of the adjoining one. Any 

 of these conductors could be instantly reinoved or re- 

 placed, by which means the voltaic current could be stop- 

 ped, or the whole or any part of it be broui^ht into immedi- 

 ate activity. With a long funnel of six orifices, the whole 

 of the troughs could be filled at once. The troughs were 

 well compacted in a wooden frame and mounted on small 

 wheels. The calorific power of this machine was such as 

 to ignite fourteen inches of platina wire one third of a 

 line in diameter, in a few seconds. A steel wire of twice 



