1820.] Dr. Thomson's Analysis of Neediest one. 403 



of which of consequence cannot be ascertained. Its specific 

 gravity is 2-2. It contains 16-5 per cent, of soda, and 9 per cent. 

 of water. The other constituents are sihca and akimina, with a 

 very httle iron.* 



In the year 1811, Mr. Smithson pubUshed a paper in the 

 Philosophical Transactions to demonstrate that mesotijpe and 

 natroUte are identical. He made a comparative analysis of each, 

 and found the constituents the same. The following table 

 exhibits his analysis of mesotype, and Klaproth's analysis ot^ 

 natrolite : 



Mesotype. Natrolite. 



Silica 49-0 48-00 



Alumina 27-0 24-25 



Oxide of iron — T/o 



Soda 17-0 16-5 



Water 9-5 9-0 



102-5 99-5 



There cannot be a doubt that the two minerals analyzed 

 belonged to the same species. 



In the year 1816 a very elaborate paper on Zeolite was pub- 

 lished in "Schweigger's Journal by Dr. Fuchs, Professor of 

 Chemistry and Mineralogy at Landshut, vol. xvhi.p. 1. In this 

 paper he gives an account of a set of experiments which he and 

 Gehlen had undertaken to determine the composition of all the 

 different varieties of mesotype which they could procure. These 

 experiments occupied them three years, and led them to the con- 

 clusion that three different species of mineral are confounded 

 together in the mesotype of Haliy. These they have distin- 

 guished by the names oi' natroUte, skolezite, and mesoUte. 



1. Natrolite, as understood by Fuchs, comprehends under it 

 not merely those minerals called natrolite by Werner, but like- 

 wise a portion of the mesotype of Haiiy ; thus verifying Mr. 

 Smithson's determination of the identity of these two minerals. 

 It occurs occasionally crystallized in four-sided prisms, termi- 

 nated by low four-sided pyramids. These prisms are not rectan- 

 gular, as had been supposed by Haiiy ; for the faces r.eet at 

 angles of 91° 5', and 88° 55'. The angle which a facf. of the 

 terminating pyramid makes with the corresponding face of the 

 prism is 116° 5'. Natrolite occurs likewise in six-sided and 

 eight-sided prisms. 



Specific gravity, 2-256. It scratches glass slightly. Before 

 the blow-pipe it becomes opaque, and then melts in the exterior 

 flame into a transparent and colourless bead. It does not 

 become electric by heat. Its powder dissolves readilv in nitric 

 or muriatic acid, and forms a stifi" jelly when assisted by a 



» Klaproth's Bciirngc, t. 44. 



2c2 



