HardmAjS' — On the Carboniferous Dolomites of Ireland. 715 



acid passed in : super saturation with the acid was guarded against, 

 and the limestone was allowed to remain in the water for 40 days. 

 The liquid was then examined, and it yielded : — 



Carbonate of lime, .... . . 3-59 grains. 



,, magnesia, . . . . 0"47 „ 



iron, .... . . trace. 



I 



4-06 



This, calculated according to the percentage of carbonate of lime in 

 the rock, would give for the proportions dissolved : — 



Carbonate of lime, . . . . . . 79-89 



,, maa'uesia, 9 •34 



89-23; 



there being in the rock as much as 12-71 of carbonate of magnesia: 

 so that in this case also it will be seen that the result must be a 

 gradual increase in the amount of that constituent. 



It will be noticed also, that although the experiment was not con- 

 tinued for quite so long a period as I^o. 2, the total amount of car- 

 bonates dissolved is more than double. 



I^xp. 5. — The fragments of limestone from Shandon, used in the 

 last experiment, were subjected to the further action of carbonic 

 acid, in the same way, the action being allowed to go on for 20 

 days. The solution being then examined yielded the following : — 



Carbonate of lime, 1-15 grains. 



,, magnesia, 0-11 ,, 



,, iron a trace. 



Total dissolved, . . 1-26 



Calculated as before, the percentage dissolved will be in the pro- 

 portion — 



Carbonate of lime, 79-89 



,, maancsia 7-64 



a result sxifficiently near that of the former experiment. The total 



amount dissolved in this case is not quite half that dissolved in double 



the time in the former experiment. 



These investigations prove the following points : — 



1°. That in a weak solution of carbonic acid, limestones in the- 



mass, not powdered, yield more carbonate of lime than of magnesia. 



