4818.] respecting the Specific Gravity of Crystals. 133 



leave the octohedron of a greater or less magnitude, or may 

 detach from it a greater or less quantity of fragments ; and, 

 according as any portion be left to form part of the octohedron, 

 or be chipped off along with the " corners," it will have its 

 specific gravity increased or diminished. It also follows as a 

 necessary consequence of Mr. Daniell's very " unexpected " 

 discovery, that the specific gravity of crystals may be changed 

 merely bi/ their apposition to each other, and that this depends of 

 course upon the volition of the operator. Every one knows 

 that an octohedron may be converted into a rhomb by the addi- 

 tion of two tetrahedrons to two of its opposite faces ; we learn, 

 however, from these very curious experiments, that the specific 

 gravity of the rhomb is less than that of the tetrahedron, and this 

 again less than that of the octohedron ; so that two crystalline 

 forms, when placed side by side, and thus made to assume a 

 third form, produce a body which has a less specific gravity 

 than either of those which compose it. If I were disposed to 

 enter into any speculations on the subject, I might remark upon 

 the awkward consequences which may arise from this interfe- 

 rence of the volition of the operator, with the results of his expe- 

 riments ; we shall in future not only have to guard against false 

 weights and scales, or incorrect observations ; but we shall be 

 exposed to false facts and incorrect statements, which although 

 not to be suspected in the present instance, might occur from a 

 less respectable or a less cautious quarter. 



The ingenious author has, apparently, left the subject incom- 

 plete, in not stating whether this curious property of the specific 

 gravity, changing with the change of form, takes place in other 

 bodies as well as in crystals ; whether, for instance, an octohe- 

 dron of gold is specifically heavier than a tetrahedron of that 

 metal. It would seem to be a necessaiy consequence of the 

 very curious discovery of Mr. Daniell, that this should be the 

 case ; but where the results of the former experiments were so 

 very " unexpected," it would be rash to offer an opinion, until 

 the trial had actually been made. If this should prove to be the 

 case, the same correction of the specific gravities of all solids, 

 and we may presume of all fluids, will be necessary, as has been 

 noticed above with respect to crystals ; and we must hope that 

 the learned discoverer will prosecute the plan on which he lias 

 so successfully entered, and favour the world with an account of 

 the specific gravities of all bodies arranged in the same form with 

 those of fluor spar. 



The consequences which seem necessarily to flow from Mr. 

 Daniell's discovery are so very wonderful, that I at first sus- 

 pected I must have misunderstood some of the terms employed 

 by him ; or thai, in this age of innovation, he might have lifted 

 Rome new and improved nomenclature ; but the clear manner in 

 which he expresses himself seems to preclude this supposition. 

 Nor is it powsible to iuny;ine that he can have operated upon 



