12 



and to which Wohler has assigned the formula Si 4 H 4 O 5 (Si=21). 

 If it be assumed that this conclusion is correct, the further inference 

 is that the bodies are similarly constituted. On this hypothesis, to 

 arrive at the atomic weight of graphite, the total weight of carbon, 

 132, is to be divided by 4, which gives the number 33 ; and for the 

 formula of the body, putting Gr=33, we have Gr 4 H 4 O 5 . 



This conclusion is confirmed in a remarkable manner by the spe- 

 cific heat of graphite. The specific heat of the elemental bodies 

 varies inversely with their atomic weight. This law is so well 

 established, that Regnault has even proposed to determine the 

 atomic weight by it exclusively. There are, at any rate, only two 

 numbers which can be assigned as the product of the specific heat 

 into the atomic weight of the elemental bodies, namely, approxi- 

 mately the numbers 3*3 and 6*6. But to this law there is one sin- 

 gular exception. Carbon in all its forms is anomalous. The specific 

 heats of diamond, graphite, and wood-charcoal are each different, 

 and taking the atomic weight of carbon as 6 or 1 2, no one is accord- 

 ant with the law. The specific heat of graphite is 0*20187. Now, 

 taking the atomic weight of graphite as 33, we have 33X201 =6'63, 

 a result in accordance with the law. The inference is, that the 

 assertion that 33 is the atomic weight of graphite is not only a con- 

 venient expression of chemical analysis, but corresponds to a phy- 

 sical fact. 



May 19, 1859. 



Major-General SABINE, R.A., Treas. and V.P., in the Chair. 

 Professor Henry Darwin Rogers was admitted into the Society. 



The following communications were read : 



I. " On the Alloys." Part I. "The Specific Gravity of Alloys." 

 By A, MATTHIESSEN, Ph.D. Communicated by Prof. 

 WHEATSTONE. Received May 17, 1859. 



(Abstract.) 



Before commencing a research into the electric conductivity of 

 alloys, the author deemed it requisite, as a preliminary step, to 



