Geoscience Reference
In-Depth Information
whizzing), unusual weather, seasickness, and frequent reports of two dis-
tinct sensations: the first tremulous, the second concussive (what “the coun-
try people” called “the 'thud'”).
Meanwhile, the BAAS's Earthquake Committee busied itself with prepar-
ing an alternative to human reports. J. D. Forbes, professor of natural philos-
ophy at Aberdeen, designed an instrument that would record earthquakes by
means of an inverted pendulum; David Milne named it a “seismometer.”
16
By 1841 the committee had supplied Comrie with ten such instruments,
but it soon became clear that the machines were less sensitive than Comrie's
residents themselves. In the first half of 1841, for instance, the seismometers
registered only two tremors, while their human keepers felt twenty-seven.
17
Metropolitan science had yet to prove its value in Comrie.
Equally unclear was the significance of Comrie's earthquakes to the
global science of geology. At the outset, Milne was eager to test his hypoth-
esis that these tremors were a direct result of volcanic eruptions in Italy,
via some subterranean connection. It was commonly assumed that earth-
quakes in Britain must be of foreign origin; newspapers reported them thus
as early as 1824 and as late as 1957.
18
Fortunately, Milne soon had the
benefit of Charles Darwin's experiences abroad: “there are many regions
in which earthquakes take place every three & four days,” Darwin wrote
him,“& after the severer shocks, the ground trembles almost half-hourly
for months.—If therefore you had a list of the earthquakes of two or three
of these districts, it is almost certain some of them would coincide with
those in Scotland, without any other connection than mere chance.” Milne
replied: “I am much obliged to you for warning me against too ready a
belief in the connection between earthquakes felt on opposite sides of the
equator . . . I am beginning to be sceptical as to any connection between our
Scotch earthquakes and those in Italy.”
19
on the other hand, Darwin lent
support to Milne's suspicion that earthquakes bore some relationship to
weather. the veteran of the
Beagle
voyage cited South American natives on
this point. “Under the very peculiar climate of Northern Chile, the belief of
the inhabitants in such connections can hardly, in my opinion, be founded
in error.”
20
Meanwhile, Milne was on to a new theory: that the earthquakes
were caused by the conversion of underground water into steam, which
might also generate electrical activity. In short, the proper geographic scale
on which to study earthquakes was wholly undecided.
In fact, there was nothing resembling an expert consensus on what
constituted the pertinent “details” of earthquake observations. weather,
sounds, the behavior of wells and springs, atmospheric electricity, steam
