442 Miscellaneous Intelligence. 
demand in commerce. The hydrated carbonate of copper is prepared by 
double decomposition by means of sulphate of copper and carbonate of 
a. The latter is the only product which is lost: all the others, the 
iodine, iodid of potassium, mercury, zinc and copper, are re-obtained and 
may serve again in the battery or be useful elsewhere. 
Mr. Doat does not perform the reduction of the zine and copper except 
when it can be done ona large scale; for he then obtains a casting of 
brass, of greater commercial value. 
8. A Battery, called a Battery with triple contact—One element of 
this battery consists of a glass or stone ware cup, at the bottom of which 
throughout. 
4. Nautical Telegraph.—In place of the common light used as a bea- 
con and for signals aboard ships, Mr. Tréve proposes to substitute a sim- 
ler system more easy of execution. It is based on the use of illuminat- 
ing gas light by a galvanic current of induction. The lamp at the mast 
head receives the gas through a tube of vulcanized caoutchoue having 4 
spiral of copper wire within, and covered exteriorly by some imperm 
material ; it terminates on the deck where the gasometer is placed. By 
sto] e gas can be let in at will. A Ruhmkorff’s apparatus* is 
he upper lamp 
of each of the other lamps; and are so arranged as to give a § Necks 
the beak of each burner. As the light will take place only at ae stop- 
_ e ‘ * s oe 
__ 5. Light-houses and Illumination.—Lenses and Reflectors.—It i 
Known that Buffon, desirous to repeat the experiment of Archimedes with 
ored to construct a lens of water of large: 
