54 REPORT—1858. aS He 36 
similarity addresses the eye. Is there any real relation, however? In 
the First Report (1850), p. 68, &c., I have treated of the relations of 
atmospheric pressure with earthquakes, and at p.’78 have indicated a possible 
link of connexion of a direct character between them, and shown how it is 
conceivable that local increase of barometric pressure, and diminution simul- 
taneously elsewhere, may conspire with other conditions to bring on voleanie 
action, and hence earthquake; and Perrey has hinted, in his memoir on France, 
p- 98 (4to), at some relation between his seismic mensual curves for Italy and 
Europe, having a minimum in November, and Dove’s barometric curves, 
given in Pogg. Ann. for 1843, pp. 177, 201, which show something analogous 
(quelque chose analogue). Here we observe (comparing figs. 4 and 5) the 
barometric minima very closely correspond with the seismic minima, and 
vice versd. Bearing in mind the fact, that, as the sun gets nearer the zenith 
with the advance of spring and summer, the barometer falls, and that, taking 
the whole earth together, the atmospheric pressure is less over those portions 
of its surface where it is summer, and greater over those where it is winter; 
and that these differences of pressure are greater in general as the latitude 
is lower, so that simultaneously that hemispheric surface of the globe which 
is at the time most heated by the sun is also least pressed upon by the 
atmosphere, and vice versd ; it seems warrantable to presume a cosmical and 
even a possibly direct connexion between the two phenomena; and this 
receives, again, some support* from the fact (though not without large 
exceptions), that on the whole the great earthquake bands of the world pass 
through low latitudes, where these barometric and thermic fluctuations are 
most developed. ‘ 
It would be worse than useless, however, to speculate minutely upon the — 
physical relations of those facts, in the present imperfect state of our know- — 
ledge of their connexion. $ 
The attempts which I have made to ascertain an absolute relation in — 
number, from any discussion of the Catalogue, between the recurrence of — 
seismic paroxysm at the equinoxes and solstices, and at an equal period of — 
twenty days throughout the whole range of time, have been nugatory ; it is 
impracticable to extricate a result, in which any confidence could be reposed, 
from the observational expansion and irregularities with the advance of 
time. 
We must not be discouraged, however, that after the vast labour bestowed _ 
by so many, upon cataloguing earthquakes and discussing the results, we © 
find these do not bring us even to the threshold of positive knowledge, and — 
that the main reward of toil so far, is the having cleared away rubbish, and 
at length ascertained how far lists of facts, such as have been hitherto com- 
piled from the best available materials, are of any further use. General — 
Sabine, in his Introduction to vol. iii. of the ‘ Magnetical and Meteorological — 
Observations made at Toronto,’ p. vii., when narrating the former state of © 
magnetical science as compared with its present position, says, “a few of the 
German observers had begun to note the disturbance of the horizontal force ; 
but as yet no conclusions whatsoever as to their laws had been obtained :” in 
the words of the Report, “ the disturbances apparently observe no law.” Such — 
may almost be said, as to our present knowledge of the distribution of 
earthquakes in time and in space, as referable to any natural law. We 
know how the position of terrestrial magnetism has become altered since 
the time referred to above by one of its best promoters; let us expect the 
same for seismology, and await with hope the rich flood of light that its 
ane Cee 
* See also Mylne, British Earthquakes, Edin. Phil. Journ, vol. XXXi. 
