Letvinsoii-Lessing s Classification of Rocks. 359 
spars crystallizing before the ferro-magnesian elements, as in 
the diabases and basalts. (3.) Rocks with simultaneous crys- 
tallization of the feldspars and the ferro-magnesian elements. 
The experiments of Michel-Levy and Fouque have shown that 
a fused mass held for a long time in a viscous state and quick- 
ly cooled crystallizes sometimes totally. That would take place 
in the third group. 
In general it can be concluded that: 
(1 ) The non -silicate minerals are amongst the first to 
consolidate. 
(2) In the rocks "de profondeur," and often in others, the 
ferro-magnesian minerals crystallized before the feldspars. 
(3.) In the diabases and basalts the reverse order takes 
place. 
From these facts Lewinson-Lessing tries to give the law 
of successive consolidation; and for that purpose he invokes 
the principle of maximnm zvork of Berthelot. 
Before this the same principle was applied by A. Harker 
in the Geological Magazine, 1893, P- 54^ anfl by George Beck- 
er in the American Journal of Science 1886, 3rd ser. xxxi, p. 
120. Becker says: "The sum of the chemical and physical 
transformations in any chemically active system will be such as 
to convert higher form of energy to heat, light, etc., at the 
greatest possible rate." Hence, according to Becker, the first 
minerals to be consolidated will be those that by their forma- 
tion disengage the most heat; but in a magma in process of 
crystallization heat is produced, first, by consolidation, second, 
by chemical reactions that accompany the formation of the 
mineral. 
Lewinson-Lessing takes advantage of these ideas in the fol- 
lowing manner: During consolidation most bodies lose heat 
and diminish in volume (water excepted). We will call: 
• / ' the actual specific volume of the mineral=the quotient 
•of the molecular weight by the specific weight of the 
mineral. 
v', the theoretical specific volume of the mineral accorclii'.g 
to the elements=the sum of the atomic volumes of all the 
atoms entering into the formula of the mineral. 
7', the theoretical specific volume according to the oxides 
4he sum of the volumes of all the oxides (including SiO=) 
which compose the mineral. 
