properties of the Two New Fluids in Minerals. 421 



C D E. In ordinary temperatures, about 45, there is a vacuity of 

 the size V, in the expansible or dotted fluid, and the dense, or 

 shaded fluid, occupies the necks b c, d e, DE, and also the extre- 

 mity F. By applying the heat of the hand to the specimen, the 

 expanding fluid in the branches V C, V D, finds space for itself, 

 by filling up the vacuity, but as there are no vacuities in the 

 portions of expanding fluid at A B, B, and E F, they must ne- 

 cessarily force out the dense fluid which confines them. The 

 dense fluid in the neck E D, is thus made to appear at D, and 

 the whole of the dense fluid at b c is driven off to d e, till, ac- 

 cumulating there, it is drawn by attraction to the nearest neck, 

 m n op. Here it first lines the circumference of the hollow neck, 

 from its powerful attraction for topaz ; and, as the lining becomes 

 thicker, it appears as a slight elevation between o and p, and be- 

 tween m and n. These elevations increase till they leap together 

 by their mutual attraction, and form a column of the dense fluid 

 mnpo. The column b c of dense fluid has now disappeared en- 

 tirely, and the space A B C D is filled with the expanding fluid. 

 The heat of the hand being continued, the expanding fluid A B 

 forces itself through the little cylinder of dense fluid d e, which re- 

 sumes its place the moment that a portion of the former has pas- 

 sed. But as the same heat has been expanding the fluid between 

 n p and C, which pushes out part of the dense fluid at m n o p, 

 this dense fluid, and the surplus of what was displaced from b c, 

 moves along the sides of the cavity till it occupies the portion 

 q r, of the branch V D. Sometimes the dense fluid is entirely 

 driven from m n o p, and part of it sent to the extremity C ; 

 though, in general, a very small portion remains at the very 

 neck m o. 



As the specimen cools, the dense fluid quits m o and q r, and 

 is gradually transferred through the neck d e to the neck b c ; 

 every portion of it invariably resuming the very position which 

 it had before the application of heat. 



