in Cavities of regular Crystals. -311 



ring the process of concreting into the crystalline form, had 

 surrounded a portion of the fluid in which it had been dis- 

 solved. Novv, however satisfactory this may appear in accoimt- 

 ing for some specimens, it must be allowed that there are 

 others again with regard to which it entirely fails. 



A theory may be proposed, more consistent with the ap- 

 pearances of artificial crystallization, and quite authorized by 

 a comparison of the same substances as produced by the ma- 

 nufacturer, and as found crystallized in nature. Newly formed 

 crystals contain an excess of water in their constitution : this 

 excess, provided the substance be not of a deliquescent nature, 

 must gradually lessen, till the neutral state, as we may call it, 

 be acquired. The excess of water can only escape from the 

 interior of a crystal by capillary motion ; and should there, by 

 any malfoniiation of the nucleus or any jDart of the interior, 

 be left a void space in the crystal, then the capillaiy attraction 

 may be induced internally as well as to the surface. 



When we examine natural crystals, we find them possessed 

 of a peculiar compactness of cohesion, and tardiness of solution, 

 which we do not find with regard to those artificially formed. 

 The natural sulphate of lime appears inert to water ; and the 

 natural carbonate of baryta appears equally inert to the 

 strong muriatic acid: but the artificial salts aie I'eadily acted 

 upon, the former by the water, and the latter by the acid. Not 

 only is this found to be the case, but we observe also that 

 the artificial crystals gradually acquire from age a greater or 

 less degree of the inertness of natural ones. The water of 

 crystallization, therefore, in artificial salts must be in a great 

 excess ; but were they exposed for a long-enough time under 

 similar circumstances, we need not doubt that they would ac- 

 quire the compact and inert character of natural ones. The 

 large crystals of sulphate of magnesia, when first formed at 

 the manufactory, contain more water in their constitution than 

 wlien kept some time ; and if so, how does the water escape ? 

 It must be through the pores of the salt; and the same may 

 be applied to every artificial crystal. Now, if we go back to 

 the origin of natural salts, the strong presumption of their 

 porous nature will appear. Whether we admit or deny the 

 general formation of minerals from an aqueous solution, we 

 must at least grant that many of the crystals found in nature 

 have been formed through the agency of water; and if this 

 be the case, we have no reason to believe that Nature would, 

 at the early period of the formation of these com))act crystals, 

 resort to any other mode than she at present adopts in com- 

 pleting tlie formations commenced by the manufacturer : we 



cannot 



