ae DYNAMICAL GEOLOGY. — {Boox III. 
eruptions of the Castle, Giant, and Beehive vents are marvellously _ 
impressive.’ 3 a 
In examining the Yellowstone geyser region in 1879 the author 
was specially struck by the evident independence of the vents. This 
was shown by their very different levels, as well as by their capricious 
and unsympathetic eruptions. On the same hill-slope dozens of quiet 
pools, as well as some true geysers, were noticed at different levels, — 
from the edge of the Fire Hole River up to a height of at least 80 feet 
above it. Yet the lower pools, from which, of course, had there been 
underground connection between the different vents, the drainage — 
should have principally discharged itself, were often found to be quiet 
steaming pools without outlet, while those at higher points were 
occasionally in active eruption, It seemed also to make no difference 
in the height or tranquillity of one of the quietly boiling cauldrons, 
when an active projection of steam and water was going on from a 
neighbouring vent on the same gentle slope. 
Bunsen and Descloiseaux spent some days experimenting at the 
Icelandic geysers, and ascertained that in the Great Geyser, while the 
surface temperature is about 212° Fahr., that of lower portions of the 
tube is much higher—a thermometer giving as high a reading as 266° — 
Fahr.?. The water at a little depth must consequently be 54° above the 
normal boiling-point, but itis kept in the fluid state by the pressure of — 
the overlying column. At the basin, however, the water cools quickly. 
After an explosion it accumulates there, and eventually begins to boil. 
The pressure on the column below being thus relieved, a portion of 
the superheated water flashes into steam, and as the change passes 
down the pipe, the whole column of water and steam rushes out with 
great violence. ‘The water thereafter gradually collects again in the 
pipe, and after an interval of some hours the operation is renewed. 
he experiments made by Bunsen proved the source of the eruptive 
action to lie in the hot part of the pipe. He hung stones by strings 
to different depths in the funnel of the geyser, and found that only 
those in the higher part were cast out by the rush of water, 
sometimes to a height of 100 feet, while at the same time the 
water at the bottom was hardly disturbed at all. These observa- 
tions give much interest and importance to the phenomena of 
geysers in relation to volcanic action. They show that the eruptive - 
force is steam; that the water column, even at a comparatively 
small depth, may have a temperature considerably above 212°; 
- that this high temperature is local; and that the eruptions of steam — 
and water take place periodically, and with such vigour as to eject 
large stones to a height of 100 feet. | 
‘The hot water comes up with a considerable percentage of mineral 
matter in solution. According to the analysis of Sandberger, water 
' See Hayden’s Report for 1870; Comstock’s Report in Jones’s Reconnaissance of 
N. W. Wyoming, &c., 1874. 
* Comptes Kendus, xxiii. (1846), p. 934; Pogg. Annal. \xxii, (1847), p. 159.; Txsoxain 
(1851), p. 197, Ann. Chimie, xxxvili. (1853), pp. 215, 385. 

