found in the Neighbourhood of Glasgow. 407 



water which they contain, and which is easily driven off by 

 heat. 2. Minerals nearly destitute of water, which in general, 

 though not in all cases, exist in greater quantities than the 

 zeolites, and may be often considered as constituting an inte- 

 grant portion of the substance of the mountain in which they 

 occur. 



The zeolites, including under the term one or two minerals, 

 which agree with them in containing water and in the way in 

 which they occur, amount to about fifteen species, and there 

 are several which are peculiar to these mountains, or at least 

 have not hitherto been met with anywhere else. I shall take 

 a short view of them. 



1. Stellite. This species has hitherto been observed only 

 in the rift of a greenstone rock situated on the banks of the 

 Great Canal, a little to the east of Kilsyth. The rock had 

 been blasted, and a good deal of it brought to the neighbour- 

 hood to mend the horse-path of the canal. My son acci- 

 dentally observed the stellite as we were walking on the banks 

 of the canal, and drew my attention to it. 



It is snow-white, and always in crystals, which issue like 

 rays from several centres. Each circle of crystals is firmly 

 attached to the rock. The shape of the crystal cannot easily 

 be determined, from its small size and irregularity of form. 

 It is rather harder than calcareous spar, and has a specific 

 gravity of 2*612. This exceeds that of zeolite in general, 

 showing that it contains less water than most others. But it 

 agrees with the zeolites in melting with effervescence before 

 the blow-pipe into an enamel. It is composed of 4< Cal S 2 

 4-Mg S 2 + Al S + 2i Aq, according to the analysis of myself 

 and Dr. R. D. Thomson. 



2. Thomsonite. This mineral, together with the three that 

 are to follow it, were confounded together by Cronstedt un- 

 der the name of zeolite, in his paper on the subject published 

 in the Memoirs of the Stockholm Academy for 1756. In 

 his Mineralogy he attempted to subdivide the zeolite into 

 species, but his descriptions are too imperfect to enable us to 

 recognize the minerals to which he alludes. Werner after- 

 wards divided the zeolites into needlestone, radiated zeolite 

 and foliated zeolite. Haiiy afterwards attempted a more exact 

 arrangement, and divided the zeolites into two species, which 

 he distinguished by the names of rnesotype and stilbite. In 1817, 

 Fuchs and Gehlen made an accurate chemical analysis of a 

 number of zeolites, and showed that the mesotype of Haiiy 

 contains three distinct species, which they distinguished by the 

 names ofnatrolite, mesolite and scolezite. In 1820, Mr. Brooke, 

 without being aware of what had been done by Fuchs and 



