348 Analysis of Scientific Books and Memoirs. 



This would make the specific gravity of the gas 4.2361, which only ex- 

 ceeds the specific gravity found by about one seventieth part, — a difference 

 certainly not greater than might be looked for in determining the quantity 

 of nitrous gas mixed with it. 

 The gas, then, is a compound of 



1 atom hydrogen, 0.125 

 1 atom carbon, 0.750 

 \\ atom chlorine, 6.750 



7.625 

 and its atomic weight is 7.625 



The discovery of this gas was gratifying to Dr Thomson, for the follow- 

 ing reason : — In the First Principles of Chemistry, vol i. p. 249, he 

 pointed out a remarkable property of the compound of one atom carbon and 

 one atom hydrogen. This compound he distinguishes by the name carbo- 

 hydrogen, since the appropriate term carhuretted hydrogen has been unlucki- 

 ly applied to a different combination. Carbo-hydrogen has the property of 

 forming a variety of gases and vapours, differing from each other in the num- 

 ber of integrant particles of carbo-hydrogen, which a single volume of the 

 gas or vapour contains. The gas described in this paper (abstracting the 

 chlorine) contains only one integrant particle of carbo-hydrogen in a vo- 

 lume ; defiant gas contains two integrant particles. One of the oleaginous 

 liquids obtained by condensing oil-gas, which has been examined by Mr 

 Faraday in an insulated state, but which had been previously detected in 

 oil-gas, in the state of vapour, by Mr Dalton, contains three integrant par- 

 ticles. Sulphuric ether vapour (abstracting the water) contains four inte- 

 grant particles; while the vapour of Naphtha contains six integrant particles. 

 The following table exhibits the atomic weights and specific gravities of 

 these gases and vapours. 



Simple carbo-hydrogen gas, 



Olefiant gas, or deuto- carbo-hydrogen, 



Oil-gas vapour, or trito-carbo-hydrogen, 



Ether vapour, or tetarto-carbo-hydrogen, 



Naphtha vapour of hexa-carbo-hydrogen, 



The existence of the simple carbo-hydrogen was merely hypothetic, till 

 the discovery of sesqui-carbo-hydrogen has given us an example of its ac- 

 tual existence. Thus the only doubtful part of this reasoning has been 

 shown to be actually correct. This circumstance gives an importance to 

 the discovery of sesqui-carbo-hydrogen, to which it would not otherwise be 

 entitled. 



4. Some experiments on Gold, By Dr Thomas Thomson. — A brief no- 

 tice of this paper will be found in this Journal, No. xiii. p. 183. 



5. On the Construction of Polyzonal Lenses and their combinations with 

 Plane Mirrors, for the purpose of Illumination in Lighthouses. By Dr 



