4 Da BREWSTER on the Existence of Two New Fluids 



SECT. I. On the Existence of a New Fluid in the Cavities of 



Minerals. 



In examining the cavities of crystallised bodies, I observed 

 the most striking difference in the phenomena presented by the 

 fluids which they enclosed. Impressed with the opinion that 

 the fluid was water, I tried every method of explaining, upon or- 

 dinary principles, the phenomena which were thus presented to 

 me, but the results of a more minute examination were incom- 

 patible with such a supposition, and rendered it necessary to 

 ascribe them to new fluids, possessing new physical properties. 

 In order to convey to the Society a correct idea of the methods 

 of observation, and the train of reasoning by which I was led to 

 this conclusion, I shall give a detailed account of the pheno- 

 mena, as exhibited in different minerals. 



1. Topazes from New Holland, Scotland, and Brazil 



As the cavities in the New Holland topazes are frequently 

 arranged in strata parallel or slightly inclined to its most eminent 

 cleavage, or the one perpendicular to the axis of the prism, they 

 are peculiarly fitted for carrying on this enquiry. The facility 

 with which this mineral may be split, allows us to dispense with 

 the aid of the lapidary, and to study the phenomena through 

 perfectly flat and highly polished surfaces. 



In examining these specimens with the microscope, we ob- 

 serve the cavities arranged in strata. These cavities are some- 

 times beautifully crystallised, and sometimes amorphous, some- 

 times extremely shallow, and at other times deep. They have 

 often the shape of long canals, with parallel sides and round 



