and the formation of Gypsum and Magnesian Rocks. 183 
the results just detailed that a similar result takes place when 
carbonate of lime is substituted for the carbonate of soda, the 
carbonate of magnesia formed in the presence of an excess of 
carbonate of lime retaining only three or four per cent of this 
carbonate, 
34. According to Marignac, when carbonate of lime is heated 
in sealed tubes with a solution of chlorid of magnesium to 200° C. 
ter was removed from the tubes, washed, dried, and treated 
with dilute acetic acid, which caused a violent effervescence; as 
soon as this had subsided, the filtrate, which contained a large 
excess of acid and still attacked carbonate of lime with energy, 
was separated by filtration from the undissolved residue which 
was but little more than one-fifth of the whole. The dissolved 
portion ¢ 
gn. 
silicate, by dou! 
cate of in. A 
carbonate of soda ha’ been 
© greater part of 
hydrated silicate insoluble in acetic 
digestion with hy 
onl ¢ trace of lime, and left 
\' ity to determine its 
When ¢ ast : ermine i 
in a cop; 
iors sere Nicstes by the reac- 
1 as I have elsewhere shown plays a most import- 
f sedimentary rocks,—Proc. Society, and 
Teaults of 8 series of researches 
speci aceea 
i. 
