73
Earth sciences
At the other end of the scale,
understanding of Earth processes
was making great advances. In the
Americas, Benjamin Franklin, in
addition to performing a dangerous
experiment to prove that lightning
is a form of electricity, demonstrated
the existence of large-scale ocean
currents with his investigations
of the Gulf Stream. George Hadley,
English lawyer and amateur
meteorologist, published a short
paper explaining the action of
the trade winds in relation to the
rotation of Earth, while Nevil
Maskelyne seized on an idea from
Newton and camped out for several
months in terrible weather to
measure the gravitational attraction
of a Scottish mountain. In doing so,
he figured out the density of Earth.
James Hutton became interested ingeology after inheriting farmland
in Scotland, and realized that
Earth was a great deal older than
anyone had previously thought.Understanding life
As scientists learned of Earth’s
extreme age, new ideas about how
life originated and evolved began
to emerge. Georges-Louis Leclerc,
Comte de Buffon, a larger-than-life
French author, naturalist, and
mathematician, took the first
steps toward a theory of evolution.
German theologian Christian
Sprengel spent much of his life
studying the interaction of plants
and insects, and noted that
bisexual flowers produce male and
female flowers at different times,
so they cannot fertilize themselves.
English parson Thomas Malthus
turned his attention to demographyand wrote An Essay on the
Principle of Population, predicting
catastrophe as the population
grows. Malthus’s pessimism has
proved unfounded (so far), but his
idea that a population will grow to
outstrip resources if left unchecked
was later to have a profound
influence on Charles Darwin.
At the end of the century, Italian
physicist Alessandro Volta opened
up a new world by inventing the
electric battery, which was to
accelerate advances in the decades
that followed. Such had been the
progress through the 18th century
that English philosopher William
Whewell proposed the creation of a
new profession distinct from that of
philosopher: “We need very much
a name to describe a cultivator of
science in general. I should incline
to call him a Scientist.” ■EXPANDING HORIZONS
1774
1774
1774 1788 1798
1779 1793 1799
Joseph Priestley makes
oxygen by heating
mercuric oxide, using
sunlight and a magnifying
glass; he calls it
dephlogisticated air.
Antoine Lavoisier, after
learning the technique
from Priestley, makes the
same gas, and goes on to
call it oxygène.Nevil Maskelyne
calculates the
density of Earth
by measuring the
gravitational
attraction of
a mountain.James Hutton publishes
his theory concerning
the age of Earth.Thomas Malthus
produces his first
essay on human
population, which
later influences
Charles Darwin and
Alfred Russel Wallace.Jan Ingenhousz
discovers that green
plants in sunlight give
off oxygen; this is
photosynthesis.Christian Sprengel
describes plant
sexuality in his book
on pollination.Alessandro Volta
invents the
electric battery.