548 A. ASHE ON THE PHOTOGRAPHY OF CAVITIES IN MINERALS. 



repeated tests will always give the same results, the only 

 drawback being the length of time required to make and 

 verify an observation. 



Explanation of Plate 28. 



Fig. 1. A cavity in Topaz containing : 



a. The vacuum above the condensed liquid B. 

 h. The condensed liquid showing its volume at tempera- 

 tures between 34° F. and 70° F. 

 ,, 2. The same at 84° F., showing the increase in volume of 



the liquid and the disappearance of the vacuum. 

 „ 3. Is taken at the condensation point, when the liquid was in 

 a state of effervescence. 

 a. Mixture of gas and liquid. 

 h. Liquid collecting at the bottom of the cavity. 

 „ 4. Shows the termination of the condensation, and at — 



a. Several little drops supported by surface tension on 



the liquid. 

 h. The condensed liquid. 

 „ 5. This photograph is taken at a similar point of condensa- 

 tion to that in Fig. 3, and it may be noticed that the 

 drops in their fall from the top of the cavity increase ■ 

 considerably in size. 

 „ 6. Apparatus for observing the condensation points of gases 

 contained in mineral cavities. 



Journ. QtuLett Microscopical Club, Str. 2, Vol. VII J,, Ao. 53, ^ovemhtr 1903. 



