WRITINGS OF JAMES SMITHSON. 43 



be zeolites, which I had collected in the island of Staffa, 

 having formed GLAUBER'S salt by treating them with sul- 

 phuric acid ; and I have since repeatedly ascertained the 

 presence of the same principle in similar stones from various 

 other places ; and Dr. HUTTON and Dr. KENNEDY, had like- 

 wise detected soda in bodies, to which they gave the name 

 of zeolite. 



There was, however, no certainty that the subjects of any 

 of these experiments were of the same nature as what Mr. 

 YAUQUELIN had examined, were of that species which Mr. 

 HAUY calls mesotype. 



Mr. HAUY was so obliging as to send me lately, some 

 specimens of minerals. There happened to be amongst 

 them a cluster of zeolite in rectangular tetrahedral prisms, 

 terminated by obtuse tetrahedral pyramids whose faces coin- 

 cided with those of the prism. These crystals were of a 

 considerable size, and perfectly homogeneous, and labelled 

 by himself " Mesotype pyramidee du depart, de Pay de Dome." 

 I availed myself of this very favourable opportunity, to as- 

 certain whether the mesotype of Mr. HAUY and natrolite, 

 did or did not differ in their composition, and the results of 

 the experiments have been entirely unfavourable to their 

 separation, as the following account of them will show. 



10 grains of this zeolite being kept red hot for five min- 

 utes lost 0.75 grains, and became opaque and friable. In a 

 second experiment, 10 grains being exposed for 10 minutes 

 to a stronger fire, lost 0.95 grains, and consolidated into a 

 hard transparent state. 



10 grains of this zeolite, which had not been heated, 

 were reduced to a fine powder, and diluted muriatic acid 

 poured upon it. On standing some hours, without any ap- 

 plication of heat, the zeolite entirely dissolved, and some 

 hours after, the solution became a jelly : this jelly was evap- 

 orated to a dry state, and then made red hot. 



Water was repeatedly poured on to this ignited matter 

 till nothing more could be extracted from it. This solution 

 was gently evaporated to a dry state, and this residuum 



