MEMOIR OF HAUY. 387 



sometimes in much, the greater quantity ; and this to such an extent 

 that a single mineralogical species, iron .spar (le fer spathique) for 

 instance, which is specifically a calcareous spar or carbonated lime, 

 may contain a fourth, or even third, of its weight of iron, and thus 

 become, for the metallurgist, a real mine, rather than a simple stone; 

 as muriatic spar, which is likewise a calcareous spar, may envelop 

 grains of grit (gres) in such measure as to contain little else, without 

 having the angles of its crystals changed by a single second. 



It is the same thing in our own laboratories as in that of nature. 

 In causing a mixture of two salts to crystallize, Beudant observed that 

 one of them constrained the other to blend with its crystals in a much 

 larger proportion than that furnished by itself. Which, then, of the 

 two ought to characterize the mineral? The most abundant? By no 

 means ; for, with the exception of that abundance, all the characters 

 of the product are given by the other. 



Nor is it less certain that the same substance, at the instant of passing 

 into a crystallized form, or of individualizing itself, if the expression 

 may be allowed, takes sometimes a very different form from that in 

 which it usually appears. All the efforts of chemists have failed to 

 discover in arragonite any essential matter but the carbonated lime, of 

 which calcareous spar is likewise composed ; for the small portion of 

 strontian found in the former can only be regarded as accidental ; and 

 yet the crystals of arragonite are octahedral, and those of the spar 

 rhomboidal. And here the art of man equally succeeds in imitating 

 nature, or, indeed, effects at will what nature has rarely done. Recent 

 experiments by Mitscherlich seem to prove that certain salts, in crys- 

 tallizing, take different elementary forms, according to the circum- 

 stances under which they are made to crystallize. But in the small 

 number of cases, where nature herself has produced such differences, 

 are we justified in making but one species of these several crystalliza- 

 tions? As well might we make but one of almost all the warm-blooded 

 animals, for they, too, are as identical in the chemical nature of their 

 elements as the two stones named above. An eagle and a dog have 

 the same fibrine in their muscles ; the same gelatine in their mem- 

 branes ; the same phosphate of lime in their bony structure. Like the 

 calcareous spar and the arragonite, they differ only in the form which 

 these materials have taken at the moment of constituting the indi- 

 vidual. 



Let it be remarked that what is here said imports no neglect of the 

 chemical analysis of minerals, as none certainly was ever countenanced 

 by Haiiy himself. Such analysis is quite as essential to a knowledge 

 of them as is that of their form ; it is much more important as regards 

 their uses. Haiiy maintained only that analysis is generally powerless 

 to determine the species of minerals, because it has no certain means 

 of distinguishing their accidental from their essential substances ; be- 

 cause it is not competent, as to certain classes of stones, to affirm that 

 it has detected their elements, and every day brings to light results 

 which had escaped its observation. 



Werner, long regarded by Europe as the rival and even adversary 

 of Haiiy, differed from him in effect only, in not having carried the 

 research of principles to so high a point. Hardness, fracture, tissue, 



