16 DR BREWSTER on the Existence of Two New Fluids 



If any additional evidence were wanted on this subject, we 

 have only to examine the mode in which the two portions of the 

 new fluid B, C, are united into one by a disunion of the second 

 fluid at g h, arid again separated by its reunion. Upon the ap- 

 plication of heat, the summits g, h, become more acute, and gra- 

 dually approach to each other, till they suddenly unite, and 

 force back the surface of the second fluid into the line m n n' o. 

 A portion of the second fluid, however, is retained by capillary 

 attraction, in the angular meeting of the planes, between c and 

 F, and between d and F, and also a small portion at^ a pheno- 

 menon which affords an ocular explanation of the immobility of 

 the second fluid in the terminations and angles of cavities. 

 When the fluids again cool, the surface n n' approaches to c d, 

 and when n is near c, the surface n n' of the second fluid and 

 that of the same fluid in c d, suddenly start into union, in virtue 

 of their mutual attraction, and the portions B and C are again 

 separated. 



By allowing the specimen to rest in particular positions, I 

 have often driven part of the vacuity V towards X, so as to unite 

 all the three vacuities X, Y and Z into one ; and in like manner 

 I have caused the vacuities Y, Z and part of X to disappear and 

 unite with the vacuity V. 



In order to examine the refractive power of the second fluid, 

 I made the arrangement represented in Fig. 2., and found that 

 the second fluid W always reflected less light than the new fluid, 

 and consequently that its refractive power approached nearer to 

 topaz than the new fluid. By the same means I determined, 

 that the angle at which total reflection took place at the separat- 

 ing surface from the topaz, was very nearly the same as if the se- 

 cond fluid were water. 



The fortunate circumstance of the cavities B, C, being without 

 a vacuity, and the consequent mobility of their bounding lines 

 a b c, d ef, enabled me to compare the optical properties of the 



