£8)5 ATfALTWS OF SODAUTC. 



constituent, ftnd, at first appearance, was taken for felspar, 

 to which it bears a very striking resemblance. 

 Composition This rock is composed of no less than five different fossiU, 

 * ^^ ' iiamely, t^arnet, hornblende, auj^ite, and two others, which 

 form the paste of the mass. These are evidently diHtrent 

 rotfierals; bnt in some s^>ecimen8 are ^so Hitimately blended, 

 that it required the skill Of Count Bournon to make the dis- 

 <!nmination, and ascertain their real nature. Even this dis- 

 tiui^uished mineralogist was at first deceived by the external 

 aspect, and considered the paste as common lamellated fel- 

 spar, of a greenish colour. But a peculiarity, which pre- 

 sented itself to Mr. Allan in one of the minerals, induced 

 him to call the attention of Count Bournon more particularly 

 to its construction. 

 Crystals of sah- On a closer examination of the mineral, Mr. de Bournon 

 * found, that some small fragments, which he had detached, 



presented rectangular prisms, terminated by planes, mea- 

 suring, with the sides of the prism, HO" and 70" or nearly 

 so, — u form which belongs to a rare mineral, known by the 

 «nd of another name of sahlite, from Sweden. He farther observed, inter- 

 mineial mixed along with this, another mineral ; and after somie trou- 



1>le, succeeded in detaching a mass, presenting a regular 

 rhomboidal dodecahedron. It was to this form that Mrp Al- 

 lan had previously requested his attention, 

 tesembling the Some time before this investigation, Mr, de Bournon had 

 Swedish natro- examined a mineral from Sweden, of a lamellated structure, 

 Wollaston. and a greenish colour, which, he foundj indicated the same 

 form. From this circumstance, together with some external 

 resemblance, which struck him, he was induced to conclude, 

 that our mineral was a variety of that substance. 



To that substance the name of Swedish natroUte had been 

 given, in consequence of the investigation of Dr. AVollaUon, 

 who found that it contained a large propgytion of soda. 

 Natroliteof There are few minerals, however, thatiire so totally dis- 



Kjaproih vefx tinct in their external characters as the natrolite of Klaproth, 

 different, ,11 • r» mi • 1 



and the substance we are now treatmg oh 1 he mmeral exa- 



iJiined by Klaproth occurs at Roegan *, on the Lake of Cori- 



atance, in porphyry-slate, coating the sides of veins and cavi- 



• It has been obserred also bf Professor Jameson, ia the floetz trap 

 /roclcft behind BurntUUnd. 



tiei 



