Geoscience Reference
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Figure 4.5 Title of Edmond Halley's paper on the salinity of closed
lacustrine systems (from Philosophical Transactions of the Royal Society
29, number 344 (1715), 296-300).
relaxed by drinking punch and smoking a pipe. He drew up plans for a
diving suit, but it was not until two decades later that Andrew Becker's
celebrated version was successfully tested, again in the waters of the
River Thames. And, of course, he considered aspects of the physical
nature of the Earth, its interior and its age. His St Helena years form part
of our story of geochronology, in that while there, Halley became inter-
ested in the hydrological cycle where he observed water condensing
from clouds as rain, which then made its way to the sea through rivers
and streams. Eventually, through evaporation, water returns to the
atmosphere where it forms clouds and the cycle can continue. This
cycle he described in a paper of 1691. While all this sounds obvious to
us, and now graces the pages of even the most rudimentary of geography
textbooks, this cycle and the relationship of clouds to streams and
springs was not well understood in the late 1600s.
In 1715 Halley suggested that the age of the Earth could be
derived by examining the saltiness of lakes, and published his musings
in a short paper entitled A Short Account of the Cause of the Saltness
of the Ocean, and of the several Lakes that emit no Rivers; with a
Proposal, by help thereof, to discover the Age of theWorld (Figure
4.5
).
In essence the thrust of the paper was as follows: if one was to measure
the concentration of salt contained in lakes that lacked a river exit,
over time one would find that the concentration would increase. This
would yield an actual figure in years for the age of the lakes, assuming
that they contained no salt when they first formed. This methodology
