1813.] Scientific Intelligence. \4f 



preceding classification is the confounding together, as of equal 

 importance, those substances which occur in great abundance, 

 constituting rocks, or mountains, of considerable extent, with 

 those substances which occur only in minute quantities scattered 

 through the first. No classification can be of much value to the 

 practical geognost, unless this distinction is carefully attended to. 



Article XIV. 



SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Galvanic Battery. 



On Saturday, the 2d of July, J. G. Children, Esq. put in 

 action the greatest galvanic battery that has ever been constructed. 

 It consisted of 20 pair of copper and zinc plates, each plate 6" 

 feet in length, 2 feet 3 inches in breadth. Each pair was fixed 

 together at the top by pieces of lead cut into ribbons. A sepa- 

 rate wooden cell was constructed for each pair. The plates were 

 suspended from a wooden beam fixed at the ceiling, and were so 

 hung by means of counterpoises that they could be easily raised 

 or let down into the cells. The cells were filled with water, 

 containing a mixture of sulphuric and nitric acids. At first the 

 acids amounted to l-60th of the water ; but more was gradually 

 added till it amounted to the 30th. Leaden pipes were attached 

 to the two extremities of the battery, and conveyed the electri- 

 city out of doors to an adjoining shade, where the experiments 

 were made. The power of this battery was very great ; though 

 I am not certain whether it increased in proportion to the size of 

 the plates. It ignited about six feet in length of thick platinum 

 wire. The heat produced was very intense. It melted platinum 

 with great facility. Iridium was likewise melted into a globule, 

 and proved to be a brittle metal. The ore of indium and 

 osmium was likewise melted, but not so completely. Charcoal 

 was kept in a white heat in chlorine gas, and in phosgene gas; but 

 no change took place in either of these gases. Neither tungsten 

 nor uranium underwent any change. A very singular fact was 

 pointed out by the sagacity of Dr. Wollaston, and succeeded 

 upon trial. A greater length of thick platinum wire was ignited 

 than of platinum wire of a much smaller size. This Dr. Wol- 

 laston had previously ascertained in his own minute galvanic 

 batteries, consisting of a single pair of small plates. 



II. Volatility of Cerium. 

 The volatility of this metal, which had been previously 



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