8 
M. Berzelius on the Chemical Composition 
In order to avoid the first, I selected the mesoline, which oc- 
curs in the smallest cavities in the form of the head of a pin, 
but whose exterior surface still contains lava. This mineral 
loses on the fire 18.19 hundredths of its weight of water. Its 
composition gives 
Silex 
47.50 
Contains of Oxygen, 23.88 
No. of Equivalents, 18 
Alumine, 
21.40 
10.00 
9 
Lime, 
7.90 
2.20 
2 
Soda, 
4.80 
1.23 
1 
Water, 
16.19 
16.16 
14 
97.79 
This result contains an excess of silex and of soda. The first 
is derived from an accidental mixture of lava, which makes the 
silex obtained by the analysis greyish. The last is only appa- 
rent because the soda contains potash, of which I have not 
thought it necessary to determine the precise quantity, since it 
is too small to alter the calculated result. In neglecting it, the 
composition of this mineral may be represented by NS^ -f- 9iCS* 
S. Mesolite or Needlestone from Faroe. This mineral loses 
in the fire 1S.3, and its analysis is as follows : 
Silex, 
46.80 
Contains of Oxygen, 23.54 
Np. of Equivalents, 18 
Alumine, 
26.50 
12.37 
9 
Lime, 
9.87 
2.76 
2 
Soda, 
5.40 
1.38 
1 
Water, 
12.30 
10.93 
8 
100.87 
This result is precisely the same which MM. Gehlen and Fuchs 
obtained from their analysis, (see Arm. of Phil. vol. xvi. p. 406.); 
and the formula NS^ + 9^CS^ + 9AS^ + SAq, does not differ 
from the mesoline, but in containing 6 proportions less of water. 
4. Mesotype from Kilpatrick This is probably the same 
substance which that learned mineralogist Mr Brooke first dis- 
tinguished from the mesotype of Auvergne, by giving it the 
name of Thomsonite, and which Dr Thomson has analysed with 
his usual accuracy. The Thomsonite loses in the fire 13.1 of 
its weight, and contains 
Dr Brewster was indebted for the specimens of this mineral which he sent to 
M. Berzelius, to the liberality of Mr Edington of Glasgow. 
