.GEOLOGY — RESULTS OF CHEMICAL ANALYSES. 75 



nesia by ignition. The residue, if any, was treated with hot water, which dissolved the alkaline 

 chlorides ; these were then tested for by the usual methods. Magnesia being absent when 

 alkalies were found, their quantitative estimation was conducted in the same manner, with the 

 exception that the baryta was precipitated by adding sulphuric acid in slight excess. From the 

 filtrate the iron and alumina were precipitated by ammonia and separated, after igniting, weigh- 

 ing, and redissolving in hydrochloric acid, by caustic potassa. The lime by oxalate of ammonia, 

 the filtrate evaporated and ignited left the alkalies in the state of sulphates. If the alkalies 

 were absent the mineral was easily decomposed by digesting for several hours with concentrated 

 hydrochloric acid, and the different substances separated by the method stated. The water was 

 estimated by igniting the substance after drying, at 212° Fahr., for forty-eight hours. In de- 

 termining the specific gravity, coarse fragments of the specimens were put in a specific gravity 

 flask, partially filled with water, and placed under an exhausted receiver, thus expelling the air 

 from the porous mass. The temperature at which this determination was made was 15° C, 

 or 59° Fahr. 



In the following arrangement of the results of analysis, all from A to G are friable tufas, 

 unchanged by action of water ; H is a specimen of incrustation, while all the remainder have 

 been changed more or less by the action of the thermal springs ; and, in consequence, have 

 acquired greater hardness. Both the changed and unchanged have no cleavage, but break into 

 irregular fragments, having an uneven and hackly fracture. 



A has a specific gravity of 2.2505 ; of fine granular structure ; color, yellowish, ochreous. 

 from sesquioxide of iron; with numerous irregular nodules of clear quartz crystals, and quartz 

 colored by iron and manganese interspersed through the entire mass. No cleavage, breaks into 

 irregular fragments ; fracture uneven, opaque, very soft and friable. 



COMPOSITION. 



Si. 54.386, Al. 20.665, Fe. 9.945. 

 6a. 1.894, H. 12.919 = 99.507. 



B. Specific gravity, 2.1947; coarsely granular; fracture uneven; color, whitish gray, resem- 

 bling gray sandstone in appearance very much ; easily crushed. 



COMPOSITION. 



Si. 80.837, Al. 6.401, Fe. 4.680. 

 Ca. .384, H. 6.932 = 99.234. 



C. Specific gravity, 1.950 ; finely granular ; color, white ; resembles chalk not only in color, 

 but in fracture and softness. 



COMPOSITION. 



Si. 84.721, Al. 1.704, Fe. 4.589. 

 Ca. 1.009, H. 7.977 = 100. 



D. Specific gravity, 2.2466 ; coarsely granular ; irregular fracture ; color, reddish ; resem- 

 bling specimen B very much in texture and friability, but owing to a larger per cent, of 

 sesquioxide of iron, it is more nearly a red sandstone. 



