A new Fluid discovered in the Cavities of Minerals. 395 



the manner described by me, on the approach of the flame of the 

 spirit lamp ? 



The phenomena recorded cannot by possibility be explained 

 on the principles of his hastily assumed opinion ; and, moreover 

 he seems totally ignorant of M. Desseignes' experiments, and 

 of that of Seebeck ; by which 'tis clear, heat alone excites Vol- 

 taic action and electro-magnetic phenomena. And why should 

 it seem strange that the same agent (caloric) might modify mag- 

 netic exhibitions when excited and in action ? 



I do not know what is meant by introducing the posthumous 

 priority of the young neophyte of "nine years old." 



Yours most obediently, 

 J. Murray. 



A NEW FLUID DISCOVERED IN THE CAVITiES OF MINERALS. 



A new fluid, of a very singular nature, has been recently 

 <iiscovered by Dr. Brewster in the cavities of minerals. It 

 possesses the remarkable property of expanding about 30 times 

 more than water ; and by the heat of the hand, or between 75 

 and 83, it always expands so as to fill the cavity which contains 

 it. The vacuity which is thus filled up is of course a perfect 

 vacuum; and, at a temperature below that now mentioned, the 

 new fluid contracts, and the vacuity re-appears frequently with 

 a rapid effervescence. These phenomena take place instan- 

 Jtaneously in several hundred cavities seen at the same time. 

 The new fluid is also remarkable for its extreme volubility, 

 adhering very slightly to the sides of the cavities ; and is like- 

 wise distinguished by its optical properties. It exists, however, 

 in quantities too small to be susceptible of chemical analysis. 

 This new fluid is almost always accompanied with another 

 Jluid, like water, with which it refuses to mix, and which does 

 not perceptibly expand at the above-mentioned temperature. 

 It is a specimen of Cymophane, or Chrysoberyl. Dr. Brewster 

 has discovered a stratum of these cavities, in which he has 

 reckoned, in the space of |th of an inch square, thirty thousand 

 cavities, each containing this new fluid ; a portion of the fluid 

 like water, and a vacuity besides. All these vacuities simul- 

 taneously disappear ut a temperature of 83. If such a fluid 

 could be obtained in quantities, its utility in the construction of 

 thermometers and levels would be incalculable. There are 

 many cavities in crystals, such as those opened by Sir Hum- 

 phry Davy, which contain only water, and which, of course, 

 never exhibit any of the properties above describetl. An ac- 

 count of these results was read before 1 lie Royal Society of 

 Edinburgh on the 3d and 17th of March. — Edinburgh Phil. 

 Journ. 



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