jglS.] on a slender Platina Wire. 293 



but I am informed bv Mr. Cuthbertson tbat he has occasionally 

 splintered iron wires; and I find that Mr. Brook no iced the 

 same circumstance with steel wire, in two experiments out of 

 TJ, published in the year 1797. The splinters he produced 

 are described as about T Vth of an inch long. 



I shall not at present speculate on this phenomenon, which 

 seems to prove, by the expansive effect produced, that in cer- 

 tain cases at least electricity passes through the substance of 

 solid matter; and in such passage displays most unequivocally 

 the action of a material power. 



I remain, Sir, yours, &c. 



Princes-street, Cavendish-square, G. J. Singeb. 



August, 9, 1813. 



Article XI. 



On the Daltonian Theory of Definite Proportions in Chemical 

 Compounds. By Thomas Thomson, M.D. F.R.b. 



(Continued from p. 171.) 



We have no data for determining the composition of the 

 phosphurets, those only excepted which have been given m a 

 preceding- part of the table. No metallic carburets are known 

 to exist. a There can be little doubt that plumbago is m tact a 

 'pure charcoal, and that the small quantity of iron which it 

 contains is only accidentally present. A carburet of iron, sup- 

 posing it composed of an atom of each element, would consist ot 



Iron 89-875 



Carbon. 10*125 



100-000 



But we arc not acquainted with any such compound. Messrs. 

 Allen and Pepya found that 100 parte of plumbago, when 

 burnt, left a residue of 5 parts. If we suppose this residue to be 

 peroxide f iron, it will be equivalent to 3'45 parts of iron. 

 According to this statement the plumbago consisted of 96\55 

 parts „1' charcoal and 8'4* part* of iron. This amounts to about 

 V48 atoms of carbon combined with 1 atom of iron. We may 

 be quite certain that bo great a number of atoms ol carbon never 

 could come in contact with one atom of iron, and that therefore 

 Mich B compound cannot exist: besides, we are not sure that 

 tliis residue consisted of oxide of iron. Schra'dcr, in an analysis 



