1876.] Geology and Paleontology. 245 
voir a. The force thus expended, a vacuum is produced in b by the re- 
ceding of the column of water in a, and the foregoing operations are 
indefinitely repeated. This theory seems capable of explaining the facts 
so far as they are known, and the variations observed in special cases, or 
_ even in different eruptions of the same geyser, appear to the writer to 
require but slight modifications of the section, and none that are of great 
importance. The passage c may be kept filled with water by means of 
the surplus which falls back into the bowl. 
“ Bunsen’s theory of geyser action, which has not yet been proven inade- 
quate to explain the more prominent features of eruptions, does not seem 
sufficient (to the writer) to account for all the differences between the 
geyser and the mere hot spring, but it must not be inferred that such ex- 
cellent authority is disregarded. On the contrary, the author proposes 
the structural hypothesis simply as a supplement to the superheating 
theory of Dr. Bunsen, in order to explain surface phenomena common in 
the Fire-Nob basins, which appear to require an extension of his views. 
At the same time it must be confessed that there are objections to his the- 
ory, based upon these observations, which are difficult to reconcile. It 
will be impossible to present these here, but an outline of the theories 
in question is appended. Bunsen has shown that an eruption may be 
artificially produced by introducing steam near the base of a long, nar- 
row column of water, which causes the water, as it rises under pressure, 
to become super-heated, the surplus heat being used for the production 
of more steam, which adds to the elevating force. This admirable the- 
ory, of which the above experiment is an illustration, is based upon a 
series of ingenious observations among the hot springs of Iceland. 
Bischof adopts an opinion almost identical with the structural hypothesis 
here proposed, and the present author, it will be remarked, combines the 
two theories, believing both necessary to explain all the facts observed.” 
Tar MECHANISM or STROMBOLI. — As apropos to the subject of gey- 
sers we would direct the reader’s attention to an able article on Stromboli 
by the late- G. Poulett Scrope, published in the Geological Magazine for 
December, 1874, and illustrated by a view of Stromboli, which is here 
reproduced (Plate I.) through the courtesy of the publishers, the Messrs. 
riibner & Co. Mr. Scrope attacks Mallet’s suggestion that the mech- 
anism of Stromboli has not merely some similarity with that of a geyser, 
but that the volcano actually contains a geyser in its inside. In this con- 
nection he quotes Lyell’s Principles, in which it is stated that the phe- 
nomena of geysers “have no small interest as bearing on the probable 
mechanism of ordinary volcanic eruptions, namely, that the tube itself is 
the main seat or focus of mechanical force.” Scrope then refers to his 
wn theory, which corresponds to the views of Lyell and Dana. The 
ae of the latter he quotes as that “of an impartial and unquestionable 
authority ” , . Mr. Scrope shows that 
“ there is bipes ee mig aid wi g Str mbli any mech- 
: ground whatever for attributing to Stro y 
‘nism different from that of ordinary volcanoes.” 
