46 THE GEYSERS OF PLUTON RIVER, 
around you are rapidly dissolving under the powerful 
metamorphic action going on. Porphyry and jasper 
are transformed into a kind of potter’s clay. Pseudo- 
trappean rocks are consumed much like wood in a slow 
fire, and go to form sulphate of magnesia and other 
products. Granite is rendered so soft that you may 
crush it between your fingers, and cut it as easily as 
unbaked bread. The feldspar appears to be converted 
partly into alum. In the mean time the boulders and 
angular fragments brought down the ravines and river 
by floods are being cemented into a firm conglomerate ; 
so that it is difficult to dislodge even a small pebble, 
the pebble itself breaking before the conglomerate 
yields. 
“The thermal action on wood in this place is also 
highly interesting. In one mound I discovered the 
stump of a large tree silicified; in another, a log 
changed to lignite or brown coal. Other fragments 
appeared midway between petrifaction and carboniza- 
tion. In this connection, finding some drops of a very 
dense fluid, and also highly refractive, I was led to 
believe that pure carbon might, under such circum- 
stances, crystallize and form the diamond. Unfortu- 
nately for me, however, I lost the precious drop in 
attempting to secure it. | 
‘A green tree cut down and obliquely inserted in 
one of the conical mounds, was so changed in thirty- 
six hours that its species would not have been recog- 
nised except from the portion projecting outside, 
around which beautiful: crystals of sulphur had already 
formed.” 
According to the statement of MacDonald, our 
