1824.] On the Power of Bodies to conduct Electricity. 39 



bite thinking it possible that it also might contain titanium ; 

 but 'it gave no indication of that metal, either when fused in the 

 reducing flame, with salt of phosphorus alone, or with the addi- 

 tion of a small morsel of tin-foil. . 



3. The Matrix, or greyish-coloured substance, in which the 



latrobite is imbedded. 



Alone in the matrass, behaves like latrobite ; appearance 



unaltered. . „ . • i • i. 



In forceps, bubbles up, and fuses into an irregular greyish. 



globule. . .i c *. 



With soda, in proper proportion to the assay, fuses into a 

 greenish-grey, semi-transparent globule, which in the reducing 

 flame is colourless. On platina foil, with soda and nitre, very 

 slight indication of manganese. 



With borax, dissolves very slowly ; globule transparent, and 

 deep-yellow, hot ; colourless, cold; in the reducing flame nearly 

 the same, but colour lighter, and more inclining to green. 



With salt of phosphorus, nearly as with borax, except that the 

 action is still slower, the yellow colour, in either flame, lighter, 

 and without any tinge of green. A silica skeleton remains 

 undissolved. , 



With nitrate of cobalt, dirty-rose colour ; the fused edges 



purple. . 



From the last result, the grey substance appears to contain a 



considerable portion of magnesia. 



I hope before long to give the analysis of the three preceding 



minerals. 



Article VII. 



Abstract of the Report on M. Rousseau's Memoir respecting a 

 new Method of measuring the Power of bodies to conduct 

 ■ Electricity. By MM. Ampere and Dulong* 



M Rousseau, who has been occupied several years in the 

 construction of dry voltaic piles, with the view to discover the 

 circumstances which modify the energy and duration of their 

 action, conceived the idea of employing those instruments to 

 appreciate the different degrees of conducting power of the sub- 

 stances arranged in the class of bad conductors of electricity. 

 For this purpose he has contrived the apparatus we are about to 

 describe! The dry pile, which forms the principal part of it, is 

 made of discs of zinc and tinsel, separated by pieces of parch- 

 ment, soaked in a mixture of equal parts of oil of popp.es, and 

 essence of turpentine; the whole ,s covered laterally With 

 resin to prevent the contact of the air. I he base of the pile 



* From the Annidei dc Chimic, 



