BY COMPRESSION, 2i 



it, tlirough which the carbonate, united with the matter of {lis 

 tube, had flowed in two or three places. The shell had 

 shrunk upon itself, so as to stand detached from the sides, and 

 bore very strong marks of fusion. The external surface was 

 quite smooth, and shining like an enamel. The internal pan 

 consisted of a mixture of large bubbles and solid parts : the in- 

 side of the bubbles had a lustre much superior to that of the 

 outside, and equal to that of glass. The general mass was serai- 

 transparent ; but small parts were visible by the lens, which 

 were completely transparent and colourless. In several places 

 this smooth surface had crystaUized, so as to present brilliant fa- 

 ccttes, steadily shining in certain aspects. I observed one of these 

 facettcs on the inside of an air-bubble, in which it interrupted 

 the spherical form as if the little sphere had been pressed in- 

 wards at that spot, by the contact of a plane surface. In some 

 chalk near the mouth of the large tube, which lay upon a sti-a- 

 tum of silex, another very interesting circumstance occured. 

 Connected with its lower end, a substance was visible, whicli 

 had undoubtedly resulted from the union of the carbonate with 

 the silex. This substance was white and semitransparent, and 

 boi-e the appearance of chalcedony. The mass of chalk hav- 

 ing attached itself to that above it, had shrunk upwards, leav- 

 ing an interval between it and the silex, and carrying some of 

 the compound up with it. From thence this last had been in 

 the act of dropping in a viscid state of fusion, as evidently ap- 

 peared when the specimen was entire ; having a stalactite and 

 stalagmite corresponding accurately to each other. Unluckily 

 1 broke off the stalactite, but the. stalagmite continues entire, 

 in the form of a little cone. This new substance effervesced 

 in acid, but not briskly. I watched its entire solution ; a set 

 of light clouds remained undissolved, and probably some jelly 

 was formed ; for I observed, that a series of air-bubbles re- 

 mained in the form of the fragment, and moved together with- 

 out any visible connection ; thus seeming to indicate a chemi- 

 cal union between the silex and the carbonate The shell, 

 fused in the experiment, dissolved entirely in the acid, witli 

 violent effervescence. 



In the three last experiments, and in several others made at 

 the same time, the carbonate had not been weighed ; but no 

 water being introduced to assist the compression^ it is proba- 

 ble there was much loss by iatcrnal calcination ; and owing 



doubtless 



