100 Mr. Mattet on the Dynamics of Earthquakes. 
as first observed in a large portion of Sweden, /i/tingly or continuously, and only 
in long periods of time perceptibly altering the level of the sea and land.”’* 
He does not attempt to assign the law of motion of any one of the several 
orders of earthquake waves. The shocks, also, he describes as either horizontal 
and vertical, or rotatory and vorticose in direction ; the two former, he says, are 
almost always observed together, the latter is rare; and instances the Calabrian 
obelisks, &c.; but, like all preceding writers, he leaves the subject without an 
attempt at explanation. 
He also gives, as another instance of vorticose or rotatory movement, the 
twisting of the previously straight furrows of ploughed fields, in the Calabrian 
plain, as recorded by Dolomieu ; confounding, in this case, the distortion produced 
by the slipping of the soil over an inclined and twisted bed upon which it reposed, 
with the true rotation of the obelisks, &c., the real nature of which I have already 
explained. 
When, however, we find Humboldt} seriously ascribing the dome-shaped 
forms of the Puy de Dome and of Chimborazo, to their being hollow bubbles of 
trachyte or dolerite, blown out by elastic vapours at some former period, we see 
the evidence that the greatest minds may be captivated by a favourite fancy, and 
feel no surprise at his adoption of the untenable, but analogous theory of Michell, 
if, indeed, such BE his view, for he leaves the subject in entire doubt. Whilst 
it is impossible to discuss at length the views of Humboldt, at the termination of 
a paper already far too long, I have deemed it necessary not to pass unnoticed the 
opinions of one whose authority is so generally reverenced. 
In having thus attempted the treatment of a vast and difficult subject, I may, 
perhaps, at times have appeared to some to wander into the regions of mere scien- 
tific speculation or romance. Iam not conscious of having done so, but if I have, 
it is pleasant to be sustained even there, and the value of occasionally giving rein to 
the imagination asserted in such words as the following, uttered by a Humboldt : 
«<A philosophic science of nature strives to rise beyond the limited require- 
ments of a bare description of nature. It consists not in the barren accumula- 
tion of isolated facts; the curious, the inquiring spirit of man must be suffered 
to make excursions from the present into the past, still to surmise what cannot be 
* Pages 224-226. + Page 238. 
