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degree of pressure we learn, that water may be so thoroughly in- 

 terspersed between, and so intimately united with, the particles of 

 bitumen, as to constitute a part of its mass. -This, htiwever, takes 

 place in the soft bitumens only, and when these substances have once 

 been deprived of the water they contain by exsiccation, they are no 

 longer capable of entering into union with it ; becoming imperme- 

 able to that fluid, with which every part had before been penetrated. 

 Thus, in many other substances, such as the balsams, gum resins, and 

 vegetable gluten, a certain portion of water enters into their original 

 composition, being a necessary constituent of the substance, whilst 

 existing in that form ; but when these substances become dry and 

 hard, water is capable of being united with them but very sparingly, 

 if at all. The Abbe Fortis, whilst describing the mine of pisasphal- 

 tum, in the isle of Bua, relates that, upon breaking the drops of 

 bitumen, which having exuded in a soft state, had become hard and 

 brittle, he found in the centre of each a drop of clear water. That 

 water exists formally in petroleum is rendered probable, by its 

 being produced in a considerable quantity by the distillation of 

 this substance. It must indeed be allowed, that, in the operation 

 of distillation, such a new combination of the principles of which 

 the petroleum is composed may take place, as may occasion the 

 formation of water ; the hydrogen and oxygen thus uniting, whilst 

 the carbon is left in the residuum contained in the retort : but that 

 water may exist in and form a part of the original substance, there 

 does not appear to be the least reason to doubt*. 



* That water may exist in an intermediate state, between that resulting from the 

 actual combination of the principles which constitute water and their state of complete 

 separation, does not appear to be improbable. In siliceous and other hard bodies, ca- 

 pable of being reduced to a pulverulent form, and in no other way manifesting the least 

 trace of it, its presence is detected by distillation. From the observations of my inge- 

 nious neighbour, Mr. Hornblower, it appears, that the current of air from an hydraulic 

 bellowsp reduced a considerably greater effect, in augmenting the intensity and brilliancy 



