Geoscience Reference
In-Depth Information
of the paper had to be produced in November 1899 as all the stocks of
the original were distributed, and demand continued. This allowed
Joly to correct a number of small errors that had appeared in the
appendix of the first impression. The paper was also reprinted in
North America in its entirety in the Annual Report of the
Smithsonian Institution for 1899, all of which allowed for rapid and
widespread dissemination of Joly's theory. This paper fired the ima-
gination of both scientific and general audiences, and for perhaps a
decade his 'sodium method' held sway amongst geochronologists.
This work was partially influential in the discrediting of Lord
Kelvin's chronology, which was beginning to fall from favour as the
great man grew older. However, in due course even Joly's work at this
time became discredited, and supplanted by the newer field of
radiogeology.
Brilliant in its simplicity, Joly assumed that when formed, the
oceans that bathed two-thirds of the Earth's surface were composed
of fresh water. But now they are salty, with varing amounts of
sodium, magnesium, and potassium salts and other materials such
as calcium chloride. These materials must have been derived from
minerals found in various rock types, which through aeons of
erosion by rainwater and seawater became released and dissolved
in these waters. Rivers, it was postulated, carried the bulk of the
sodium into the oceans, and Joly's essential assumption was that the
rates of denudation or erosion of the sodium-bearing rocks and
the discharge of the rivers into the oceans had remained uniformly
constant over geological time. So too the volume of sodium carried
each year. This uniformitarian stance was one of the fundamental
tenets of Joly's paper. The age of the Earth was derived by the simple
formula:
Mass of sodium in the ocean
Rate of annual sodium input ΒΌ The age of the Earth
To derive figures for this equation Joly turned to the oceanographic
and fluvatile findings published by Sir John Murray (1841-1914),
Search WWH ::




Custom Search