174 THE CANADIAN NATURALIST. [Juiie^ 



for, it is probable that the whole of the iron, except the small por- 

 tion of peroxyd which colors the rock, exists in the state of carbo- 

 nate. In the following analyses, therefore, the lime and the iron, 

 as well as a little magnesia, are calculated as carbonates, xiil 

 is the result obtained with four grams of the reddish portion of the 

 phonolite, as free as possible from the green ; and xiv was ob- 

 tained with two and a half grams of a mixture of the two colors. 



xiri. XIV. 



Soluble silicate, zeolite (a), by difference. 46.57 36.16 



Insoluble silicate, feldspar (b) 45.75 55.40 



Carbonate of lime 3.63 4.36 



" iron 3.52 3.72 



" magnesia 53 .36 



100.00 100.00 

 In order to fix the composition of the soluble silicate, the 

 amounts of the insoluble residue and of the separated silica, 

 alumina, and alkalies, having been carefully determined, and the 

 lime, magnesia, and oxyd of iron calculated as carbonates, the 

 water was estimated by the loss. In this way were obtained the 

 results given under xiii A, and xiv A ; while the analyses of 

 the insoluble silicate, which is a potash feldspar, are given under 

 Xlll B, and XIV B. 



XIII A. 



Silica 51.96 



Alumina 24.42 



Soda 12.93 



Potash 1.15 



Water 9.54 



100.00 100.00 100.00 100.00 

 The composition of this zeolitic mineral is intermediate between 

 analcime and natrolite ; but the readiness with which it gelatinizes 

 with acids, leads to the conclusion that it belongs, in great part at 

 least, to natrolite. The theoretical composition of these two 

 zeolites is for the sake of comparison, placed alongside of the two 

 analyses of the soluble portion of the phonolite. 



XJII B. XIV B. 



Silica 59.70 60.90 



Alumina= 23.25 24.45 



Lime 99 .45 



Potash 9.16 undet. 



Soda 2.97 " 



Volatile 2.23 2.10 



98.30 .... 



