148 



Carbonate of Lime is composed of half of a very acute 

 rhomb with three largish faces of the aequiaxe, and three 

 smaller ones, probably belonging to the primitive rhomb : 

 see geometrical figure. 



It is not a little singular that the like stones excluding 

 the trap have been found in Wiltshire at a small depth un- 

 der ground, of which I have obtained a specimen by favour 

 of the Marchioness of Bath. 



This specimen, rich with information, is particularly worth 

 the attention as well of the novice as of the adept, con- 

 sidering the curious divisions of formation in the different 

 substances of which it is composed. The part of the rock 

 this came from seems to have been a mixture, as it were a 

 chaotic one, (if I may so term it,) appearing like the frag- 

 ments of various rocks that had undergone the action of 

 moist elements, so as to form air, and water bubbles, 

 which could not immediately escape. Apparently a con- 

 tinual deposition has taken place, more still forming, and 

 enclosing the preceding till the who>e matter was deposited. 

 In the mean time each elementary substance, according to 

 the particular formation of its molecules, and the nature 

 of its nearest neighbour, formed, either by itself or into 

 combination. Thus the Carbonic Acid and Lime united 

 together, so as to construct a Crystal in the middle of this 

 hollow as complete as circumstances would admit of, de- 

 pending on the quantity of Carbonate of Lime received in 

 solution, perfecting some faces and depositing the other 

 molecules irregularly. A small tinge of Iron stained the sol- 

 vent, and consequently the Crystal towards the top is a 

 little coloured. The surrounding Quartz has also crystal- 

 lized under similar circumstances, and is somewhat stained 

 with the Oxide of Iron among the Crystals, giving this 

 lining a pinkish hue, which is again conspicuous at the 

 outer side and edge next the piece of compound rock. 



