716 Proceedings of the Royal Irish Academy. 



2°. That in equal times the more magnesian limestones are least 

 susceptible to the action of such a carbonic acid solution. 



3°. That other things being equal, the relative proportion of the 

 two bodies dissolved appears to remain fairly unaffected by the time 

 occupied in the experiment. 



I should mention that the experiments detailed above are not the 

 •only ones made which verified the above points: but it would be 

 tedious and uninteresting, I conceive, to enter into particulars of all 

 of them. 



[^Note added in Press. — In order to test the effect of more energetic 

 •acids, the following experiment was made since the foregoing was 

 written. 



A piece of dolomite from Ballyfoyle, near Kilkenny, having the 

 following composition, was taken : — 



ANALYSIS. 



Carbonate of lime, 55-48 



,, magnesia, 43'52 



Perric oxide and alumina, . . . . 0-68 



SUica, &c., 0-34 



100-02 

 Specific Geavitt, 2-73. 



Being broken up small, pieces were carefully selected, so as to be 

 as fi'ee as possible from other minerals, such as carbonate of ii'on, 

 calcite, &c. 141 grains were placed in a beaker with distilled water, 

 to which a little hydrochloric acid was added. The solution, although 

 weak, caused copious effervescence from the interstices. The experi- 

 ment was continued for about a month — a few di'ops of acid being- 

 added, when test-paper denoted that the acid previously added had 

 been neutralised. Having left home for a fortnight, I found on my 

 return that a flocculent precipitate — probably carbonates of iron and 

 lime — had been thrown down, no doubt induced by absorption of car- 

 bonic acid from the air. The addition of a few di-ops of acid dissolved 

 this. The whole was then allowed to stand for more than another 

 month; at the expiration of which time a little acid was added to 

 dissolve the precipitate that had again formed — but not enough to 

 affect the undissolved dolomite — and the solution was filtered off. 

 Both solution and undissolved residue were then carefully analysed. 



The followina' Table gives the result : — 



