. 251. CHARACTERISTIC. 389 



rieties, for the rest exactly agreeing with Amiantus, in 

 which the crystalline filaments are somewhat coarser. They 

 are no longer flexible, but still too weak to stand the ex- 

 periment of determining their hardness. Others are still 

 thicker : we may discern traces of their regular structure ; 

 yet on account of their minuteness, we cannot apply the 

 goniometer for taking their dimensions. They sink in 

 water, scratch prismatoidal Gypsum-haloide, but they 

 lose their coherence, if we try to pass them over a face of 

 rhombohedral Lime-haloide. At last we meet with va- 

 rieties, whose form and cleavage are more apparent 

 and observable, whose specific gravity is about three times 

 that of water, and the hardness between 5-0 and 6'0. 

 These allow of an immediate determination, and will be 

 placed by that process within the species of hemi-prismatic 

 Augite-spar. The mode of reasoning applied here will be 

 the following. 1 he variety preceding the last is the same 

 as that which has been determined ; those immediately pre- 

 ceding are again the same as the one immediately preceding 

 the last ; and thus we finally arrive at the Amiantus itself. 

 The determination of this mineral is effected by the assist- 

 ance of a greater or less number of varieties, interposed be- 

 tween one that is immediately determined, and another 

 which cannot be determined immediately ; the method em- 

 ployed is therefore that of the Mediae Determination. The 

 more general our knowledge of the productions of the Mi- 

 neral Kingdom, the greater facility we shall experience in 

 the mediate determination. Through this means, a great 

 number of minerals may be determined, and reduced to their 

 respective species, which could never have been ascertained 

 by immediate determination. The mediate determination 

 has indeed been hitherto very often applied, though it was not 

 clearly reduced or brought in connexion with the immediate 

 determination, upon which nevertheless both the correctness 

 and certainty of the mediate determination depends. The 

 mediate determination is peculiar to, and intimately con- 

 nected with, the natural-historical method of Mineralogy ; 

 hence we may infer, that nothing can escape this, which may 

 be determined by any other method. 



