Dr. Heddle on Mesolite and Farbelite {Mesole). 51 



the per-centage required by any mineral which can stand inter- 

 mediate between natrolite and scolezite (galactite, therefore, is 

 to be referred to one or other of these species ; and as the soda 

 greatly preponderates, it is to be considered as merely a variety 

 of natrolite, the soda mineral) ; but^ should we find that any or 

 all of the substances at present under consideration do so agree, 

 then we are entitled to consider them distinct species. 



Though the minerals mesolite and mesole are well known by 

 name, I believe there is considerable difference of opinion as to 

 whether both or either are distinct species. This may result 

 perhaps from a paucity of analyses, perhaps from the published 

 analyses having been performed on impure or even mixed speci- 

 mens ; for I am afraid, that, even after years of teaching, the 

 eye cannot discriminate some of the radiated zeolites ; it rarely 

 is here assisted by form ; colour, hardness, and specific gravity 

 do not afford much aid ; from analysis alone do we obtain de- 

 cisive information. 



I very decidedly consider mesolite and Faroelite (mesole) to 

 be thoroughly good species, and quite distinct from each other ; 

 and hope the following analyses, taken in conjunction with those 

 already published, will make this evident. 



Mesolite. — 1. From Talisker in Skye, there called cotton- 

 stone ; colour white, in delicate interlacing crystals, which, when 

 crushed, become the " mealy zeolite " of some authors. 



7377-28 

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