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Observations on Pseudomorphism. 91 



The fact that the majority of these pseudomorphs contain wa- 

 ter, is other proof lhat the heat producing the change was not a 

 dry heat, but was diffused through water. Dr. Blum does not 

 seem to recognize the fact of the hydrous character of the steati- 

 tic pseudomorphs, in his work; yet analyses have shown that in 

 very many instances the steatite is a hydrous mineral, and not 

 true steatite. Serpentine and chlorite also contain a large per 

 cenrage of water.* 



CalcSpar to Bitter Spar. — This change comes under the same 

 head with those just explained. A change of this kind does not 

 require a complete solution of the lime; for late investigations 

 have shown that molecular attractions take place at high tempe- 

 ratures, without solution of all the elements concerned in the 



change. 



Carbonate of Lead to Minium. — Minium is easily produced 

 from carbonate of lead, by means of heat. 



Andalusite, Wernerite and Tourmaline to Mica. — These 

 changes must have required the high temperature that crystal- 

 lized the mica in the metamorphic rocks. 



* The agency of hot waters and vapors in producing changes in rorks, though 

 recognized by many geologists, does not seem to have received sufficient atten- 

 tion. When we consider the numher of hot springs on (he surface of the earth 

 in regions of modern volcanic action, and in others not of this nature, when 

 we remember the many eruptions of hot water, even from subaerial volcanoes, 

 and when farther we have before our eyes the wide-spread effect of volcanic 

 action beneath the sea, can we refuse to the agency of heat, thus conveyed by 

 vapors and flowing waters, a large part at least of the various metamorphic 

 changes manifest on the surface of the earth, especially if we take into view, 



the condition of a vast volcanic region in full submarine action, its floods of melt- 

 ed rocks, its opened fissures, for a long period in action, its fountains of boiling 

 waters and rising vapors ? The whole surface of the earth evinces that this sub- 

 marine action, under an ocean's pressure, has been almost coextensive with it. 

 The vast number of dykes that traverse the rocks, suggest the same fact. Where 

 are the effects of this heat if not in these pseudomorphic and metamorphic changes? 

 Prof. Keilhau attempts to account for the crystallization of the dolomites, by the 

 hypothesis of slow molecular changes taking place at the ordinary temperature. 

 But why refuse the aid here proffered ? The fact that one part of a sedimentary 

 limestone is crystallized while another is not, is fully explained by this view; 

 while his theory serves only to increase the mystery that hangs around this subject. 

 The fact also that these crystallizations have taken place without evidence of the 

 intense heat necessary for fusion is fully explained ; for, as Keilhau states, crys- 

 tallization has been lately shown by many facts to take place without fusion or 



even softening, yet not, as this author would urge, without some increase of tem- 

 perature. 



