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A lingle cavity fometimes contains feveral 

 fcores of fuch prifms, while another fhall 

 contain but very few. 



The blow- pipe eafily melts thefe geodes 

 with the ufual phenomena of ebullition and 

 phofphorefcence, and the glafs which is the 

 refult of the fufiori is fimilar to that of the 

 zeolite of the third fpecies. A fimilar jelly 

 is likewife produced from it, and wuth equal 

 promptnefs, in acids, except that it has a lefs 

 degree of vifcofity. 



Fifth and fixth fpecies. Thefe two fpecies 

 of zeolites are contained within an argilla- 

 ceous lava, of a dark-grey colour, light, and 

 of an earthy confiftence : they both merit 

 to be diftindly defcribed. The firft fpecies 

 confills of a great number of fmall fpheses, 

 white as fnow, each occupying a cavity in 

 the lava, and varying in fize, the fmalleft 

 being fcarcely one third of a line in diame- 

 ter, and the largeft more than three lines. 

 The furface of thefe fmall fpheres is not 

 fmooth, but fomewhat rough, from an in- 



VOL. Ill, F finity 



