3 



on the Atomic Theory. 135 



weight of its volume in the gaseous state. It was clearly stated 

 by M. Gay-Lussac, in his memoir on iodine, first published in 

 1814, and translated by Dr. Thomson into his Annals for Fe- 

 bruary, 1S15. We there read, " We do not know the density of 

 the vapour of iodine ; but from experiments to be stated below, 

 I have found that the ratio of oxygen to iodine is 1 to 15.G21. 

 Now the density of a demi- volume of oxygen being 0.55179, 

 0.55179 x 15.621 = 8.6195 will represent the density of iodine 

 under the volume taken for unity *. 



Under alkalis and alkaline earths we can perceive no new de- 

 termination of any consequence. 



The section on alumina, exhibits the atomic theory, dancing in 

 masquerade among the mineral species. Thus after stating 

 Rose's analysis of felspar, he proceeds as follows : " Let us 

 suppose that all the bases are combined with silica, and in the 

 state of trisilicates, except potash, which is a quadro-silicate ; 

 and let us calculate its constitution according to that suppo- 

 sition. 



(1) 2.25 : 6 :: 17.5 : 46.666 — silica united to alumina. 



[2) 6: 8:: 12 : 16=silica united to potash. 

 3.5 : 6:: 1.25 : 2.143=silica united to lime. 

 4.5:6::0.75: 1 ta silica united to oxide of iron t." 



In spite of all this coaxing, he is pestered with an excess of 

 silica in the mineral =0.941, with which his four bases will have 

 nothing to do. 



He expresses astonishment at Mr. R. Phillips's number 3.375 for 

 alumina, not perceiving it to be his own number slightly travestied 

 in order that alum might be content with two atoms at 3.375 = 6.75, 

 instead of 3 atoms at 2.25 = 6.75. The Doctor's distress at this 

 discrepancy is truly ludicrous, and will meet with no sympathy. 



But Doctor Thomson has reserved his grand atomic ballet, 

 that" it might be performed on the three new earths, glucina, 

 yttria, and zirconia. We shall exhibit merely an entree or two. 



" Let us now calculate the composition of eudialite, on the 

 supposition that all the bases are combined with silica, in the 

 state of trisilicates, except the soda, which must be in the state 

 of bisilicate. 



* (1) 6 (atom of zirconia) : 6 (3 atoms silica):: 11.102 : 11.102 

 = silica united to the zirconia. 



" (2) 3.5 (atom of lime) : 6 (3 atoms silica) :: 9.785 : 16.77= 

 silica united to the lime. 



"(3) 4(atomofsoda) ; 4(2 atoms silica) :: 13.13 ; 13.13=silica 

 united to the soda. 



"(4) 4.5 (atom of protoxide) : 6 (3 atoms silica) :: 8.8 16 : 11.75 

 =: silica united to the protoxide of iron and manganese. 



* Ann. of Phil. v. 105. t Attempt, i. 302. 



