58 Proceedings of the 



lysis, it afforded 45 98 per cent, of silica, 21*93 of alumina, 16*15 of lime, 

 4*7 of soda, and 11*25 water. These proportions give equivalents, — silica, 

 7; alumina, 3; lime, 4 ; soda, 1 ; water, 9. The mineral, therefore, con- 

 sists of 1 equivalent of a silicate of lime and soda (where the lime is to 

 the soda as 4 to 1), 1 equivalent of a sesquisilicate of alumina, and 9 of 

 water. The calculated percentage proportions of which compound are,' — 

 silica, 46*09 ; alumina, 21*93 ; lime, 15*97 ; soda, 4*46 ; water, 11*55 ; 

 which agree closely with the analytical results. No mineral has the 

 above formula, which differs, however, from that of Faroelite (Mesole), 

 merely in the insertion of the compound 2 (Ca O, Si 0) + H O. We 

 have now to see if it he not a compound mineral, i.e., a comhiuation of 

 two minerals (being capable of expression by a rational formula, it cannot 

 be a mixture). For this purpose, let us look for an instant at gyrolite, 

 the new mineral lately discovered by Dr Anderson in Skye. That- che- 

 mist gives 2 (Ca 0, Si 3 ) + 3 H 0, as the formula of gyrolite, which re- 

 quires 15*40 per cent, of water, but admits that the mineral readily loses 

 water, and that none but specimens newly broken from the rock contain 

 so large a quantity. While I myself am strongly inclined to think that 

 even fresh specimens have an atom less of water, yet I am not at present 

 prepared definitely to assert so, but I am prepared to assert the specimens 

 of gyrolite ordinarily procurable, and such as are to be found in cabinets, 

 have more probably the formula 2 (Ca O, Si 3 ) + H — as I have ob- 

 tained many such percentage proportions of water as the following : — 

 6*417, 5'9S, 6*83, &c, the last given formula requiring 5*72. Gyrolite 

 would thus seem to be a mineral which, like lomontite, loses a certain 

 quantity of water at once on the very exposure to the air, and, like lo- 

 montite, this loss is accompanied with other changes, as of form, colour, 

 lustre, &c. ; for, when fresh, gyrolite is colourless, transparent, of a vit- 

 reous lustre, and tough ; after a short exposure it becomes white, opaque, 

 of a pearly lustre, and crumbles readily. Now, this latter formula of 

 gyrolite is the very compound which we have to add to the formula of 

 Faroelite, to convert it into the form of Uigite, as before shown. Three 

 equivalents of Faroelite, united with one of gyrolite, will give a compound 

 having the following percentage proportions : — Silica, 46*51 ; alumina, 

 21*20 ; lime, 16*62 ; soda, 4*31 ; water, 11*36 ; agreeing closely with the 

 analysis of Uigite, and giving the same formula. I have already noticed 

 that in appearance Uigite stands intermediate between the above minerals. 

 Under this consideration of the subject, therefore, Uigite is made up of 

 three equivalents of Faroelite, and one of gyrolite ; if we are not allowed 

 to consider gyrolite as having ordinarily the above formula, then Uigite 

 must stand as a simple and not a compound mineral. Mineralogy is in 

 that stage when the men of the present age have to draw the sponge 

 through many of the works of those who have gone before them, to have 

 their own in turn expunged by those who follow after. Fearing that this 



