The Quarterly Journal of Science, Literature and the Arts, July-December, 1827Various
Science
The Quarterly Journal of Science, Literature and the Arts, July-December, 1827
Various
Arts -- Periodicals; Science -- Periodicals; Technology -- Periodicals
We believe that no account of Professor Carlini’s pendulum
experiments on Mont Cenis has hitherto appeared in the periodical
scientific publications of this country: the experiments are,
however, well deserving of such notice, having been conducted with
great care, and having had a specific object in view, which object
seems to have been satisfactorily accomplished. The following
brief account of them, taken from the original memoir published in
the Appendix to the “Ephéméride di Milano” for 1824, may not be
unacceptable to those of our readers who interest themselves in
subjects of this class.
The length of the simple pendulum vibrating seconds is a [p154]
measure of the intensity of gravitation; _i. e._ of the excess of the
force of gravity over the centrifugal force. In consequence of the
ellipticity of the earth, and of the difference in the direction of
the two forces, the intensity of gravitation varies according to the
different latitudes. It also varies, in the same latitude, according
to the greater or less elevation of the pendulum above the level of
the sea; _i. e._ according to its greater or less distance from the
centre of the attracting force.
Had the earth a perfectly level surface, such, for instance, as
it would have if it were everywhere covered by a fluid, the force
of gravity, in receding from the surface, would diminish in the
duplicate proportion of the distance from the earth’s centre. In the
actual state of the globe, however, its continents and its islands
are raised above the general level of the sea by which it is only
partially covered; and if a pendulum be raised, on the surface of
the land, to a known elevation above the sea, the diminution of
gravity will not be, as in the more simple case, proportioned to the
squares of the respective distances from the earth’s centre, but that
proportion will require to be modified, by taking into account the
attraction of the elevated materials, interposed between the general
surface and the place of observation.
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