228 Scientific Intelligence. 
at through the assumption that “of the numerous possible solu- 
tions, that will be the oceurring one in Nuture which involves the 
largest amount of definite minerals and the least amount of tr 
definite paste. Calculating from this basis, he arrives at the com- 
positions of twenty Vesuvian lavas ejected at different times from 
1631 to 1868, of which the following are examples:. 
Gravina, Granatello. Della Scala. C. de S.Vito, C.de Salvatore. The Atrio. T.d.Greco, 
1631. 1631. i 1834. 1855. 
1631. 1861. 
Leucite, 38-2 33°6 40°6 41-4 39-7 36.8 34-2 
Anorthite, 0°6 6-9 9-4 0-4 11°8 116 
Magnetite, 7-14 4°45 4-9 69 97 3°35 374 
Olivi e, . tr. r. tr. --- 
Augite, 8°6 41°2 311 25°1 27-4 98°T 304 
Hornblende, tr. ae: Beet tr. ae 
ica, tr. Se ees ie eee ee rae -- 
Nephelite, 105 10-0 65 8-6 11-2 11°5 10°9 
ite, tr. tr. tr. pele Paes 
Apatite, Boe 0.44 11 pot ne tr 
ste, 8-96 9-71 8-9 8°6 11°2 9°6 916 
100°00 = 100-00 100-0 100°0 100°0 100°0 10000 
* phelt or 
lite; then the magnesia mineral, augite ; and lastly magnetite and 
anorthite, al 
The analysis of the Vesuvian augite which is taken for the cal- 
culations is that of Weddin , of augite from a lava of 1631, giving 
constituent augite—one of the four always present—is hence one 
source of uncertai such calculations, for the ma reese 
in his 
results) will differ widely in the two cases. Further, the oie 
to 
re 
ae that the calculated percentage of anorthite 1m seve ad 
sa anaes results is below the actual amount present 
