424 Mr. J. A. Phillips's Notes on the Chemical Geology 



a large area having become reduced to this pasty condition, it 

 has iiovved down the side of the elevation and become deposited 

 in layers on the low ground near its base. It was also ob- 

 served in one of the ravines that mud resulting from the upper 

 springs had sometimes flowed over and choked those lower 

 in the series; and this appears to have given rise to the forma- 

 tion of fresh openings, and the progressive movement of the area 

 of greatest activity up the side of the declivity. 



About a mile to the west of these springs a high granitic 

 mountain is traversed by an immense dyke of obsidian, which, 

 having broken through it, has flowed for a considerable distance 

 into the valley. 



At the eastern foot of the hill on which is situated the first 

 group of springs are numerous others in a much more active 

 state. Here the ground is covered over a large extent by innu- 

 merable cones of plastic mud, varying from a few inches to three 

 feet in height ; these rise above the surface of a barren steaming 

 swamp, and give issue to jets of watery vapour and streams of 

 boiling water. In some cases these springs, instead of issuing 

 from small cones as above described, evolve large quantities of 

 steam and gas under the surface of water contained in basin- 

 shaped reservoirs produced by their agency in the decomposed 

 granite in which they are situated. By these means are formed 

 a multitude of seething caldrons, in which the rapid ebullition 

 of water keeps the mud in a constant state of suspension; and 

 this is either white or of a reddish colour, in accordance with the 

 amount of ferruginous matters present. To the east, at a dis- 

 tance of some three or four miles, were seen high ranges of evi- 

 dently basaltic hills, the whole district being totally uninhabited 

 except by a few Indians, some of whom were met with collecting 

 oxide of iron to be employed as paint. 



The appliances at command in such localities arc usually of a 

 limited character; but I was enabled to ascertain by means 

 of litmus-paper that the water of all the springs examined had 

 an acid reaction ; and having filled a pint bottle with water 

 from one of the largest of the basins, it was brought to England 

 for analysis. 



This amount, although manifestly too small to allow of a very 

 accurate analysis, was sufficient to admit of the estimation of all 

 the principal constituents. The following are the respective 

 quantities of the different bodies present, calculated on an impe- 

 rial gallon of the filtered water . — 



