ANALOGY OF GLACIERS TO LAVA STREAMS. 
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streams, and this ease was pressed on my attention by an unexpected journey which 
I soon after undertook to Italy and Sicily. 
§ 2. Analogy of Glaciers to Lava Streams. 
There is something pleasing to the imagination in the unexpected analogies pre- 
sented by a torrent of fiery lava and the icy stream of a glacier. But when we look 
upon the comparison historically and critically, and find how generally this analogy 
has been perceived and adverted to by persons of very different views and talents of 
observation, we are strongly tempted to suspect that some latent cause confers the 
marked resemblance. 
This cause I of course consider to be the laws and condition of their motion, the 
struggle of a semi- fluid mass of enormous weight creeping down a mountain side, in 
which fluidity and solidity are so curiously combined, that we should be at a loss in 
either case how to name it ; a straining, crackling, splintering solid, heaved on by 
the internal energy of the latent fluidity which pervades it, and which at last succeeds 
in giving to the general character of the motion and the moving mass, those of fluid 
bodies subject to the law of gravity ; whilst the parts, themselves almost rigid, have 
that rigidity most fantastically subjected to the action of the dominant principle. 
In illustration of what has now been said, I shall quote passages from some authors 
which, without particular research, have come under my notice expressive of the 
analogy just mentioned. 
Mrs. Starke, the author of a well-known guide book of Italy, published many 
years ago, speaks of having seen near the crater of Vesuvius in 1818, “five distinct 
streams of fire issuing from two mouths, and rolling wave after wave slowly down 
the mountain with the same noise (?) and in the same manner as the melting glaciers 
roll into the valley of Chamouni ; indeed this awful and extraordinary scene would 
have brought to mind the Montanvert, had it not been for the crimson glare and ex- 
cessive heat of the surrounding scoriae*.” 
Mr. Auldjo, an intrepid alpine traveller, writing about Vesuvius, in 1832, says, 
“ The field of lava in the interior of the crater, inclosed within a lofty and irregular 
bank, might be likened to a lake whose agitated waves had been suddenly petrified ; 
and in many respects resembles the Mers de Glace, or level glaciers of Switzerland, 
although in its origin and materials so very different'!'.” And the view in the same 
work of “streams of lava on the south-east of the cone” presents a perfect analogy 
to a glacier, bearing on its surface three medial and two lateral moraines. 
Captain Basil Hall, writing of Vesuvius at a later period, uses these remarkable 
expressions whilst describing an eruption of lava : — “ The colour of this stream was a 
brilliant pink, much brighter at the sides than in the middle, where either from the 
cooling of the surface, or the accumulation of cinders and broken pieces of stone, a 
* Starke’s Traveller’s Guide, Ninth Edition, p. 293. 
t Auldjo’s Sketches of Vesuvius, p. 10, published 1833. 
