The Locomotive - Lighthouse Survival Blog

110 THE LOCOMOTIVE. [July
without them the fine microscopes and gigantic refracting telescopes of the present day
would be utterly useless. About the time that Hall discovered the possibility of making
achromatic prisms, Ernest Stahl proposed the theory of '• phlogiston," to account for
various chemical facts. This theory had been .stated also by Becher, who died in 1682;
but Stahl did so much to establish it that he is commonlj' regarded as its originator.
"Stahl imagined that all bodies which would burn contained an invisible substance
which, he called ' phlogiston,' and that when a body was burned it gave up its phlogiston
into the air." 'Ehis, as we now know, was a very erroneous idea; but Stahl and his con-
temporaries and successors explained so many facts by it, that chemists believed in it for
many years. In 1732 Du Faye showed that there are two kinds of frictional electricity,
one obtained by rubbing glass, and the other by rubbing sealing wax. In 1788 Bouguer
first determined the density of the earth, by finding out how the attraction of a high
mountain in Peru compared with the attraction of the whole earth. About the same
time the celebrated Swiss mathematician Daniel Bernouilli first proposed the molecular
theory of gases, a theory which is now universally accepted. He taught that gases
consist of innumerable little particles of matter flying about in every direction, and that
the pressure of a gas is due to the incessant bombardment of the walls of the containing
vessel by the flying molecules composing the gas. In 1740 Lazzaro More gave a clear
and correct account of the history of the fossils that we find in rocks. In the same year
(1740) Hawksbee constructed his electrical machine, in which, for the first time, a globe
of glass was substituted for the usual suljihur glol^e, and silk was used as the rubbing
material. In 1741 Linnaeus founded his botanical gardens in L'psala, which have served
as a model for many other like gardens, such as those at Kew, England. Albert
Yon Haller published a beautiful set of anatomical drawings, between 1743 and 1753,
which were from dissections by himself ; and during the course of these dissections he
discovered the way in which muscles contract. It was not far from this time that
Fahrenheit and Reaumur devised the thermometric scales now known by their names,
and Celsius devised the centigrade scale. In 1746 Franklin began to experiment with
electricity, and soon afterwards proposed his "one fiuid" theory. About this time
Haller took up the study of comparative anatomy, and John Hunter devoted his whole
life to it. Others had compared the structure of man and animals, but Haller and Hunter
were the first to make a systematic study of the subject. About 1749 BuiTon's great
work on natural history was published, and this, though it contained many mistakes,
gave a great impetus to the study of animals. In 1752 Franklin made his celebrated kite
experiment, drawing lightning from the clouds, and proving its identity Avith electricity.
He also invented the lightning rod. In 1753 Linnaeus introduced the specific names by
which the various species of plants and animals are distinguished from one another. In
1754 Bonnet made his celebrated experiments on the leaves of plants. In 1756 Black
discovered carbonic acid gas. He showed that it combines with quicklime to produce
lime carbonate; and because the lime "fixed" it, he called it "fixed air." for want of a
better name. DoUancVs invention of the achromatic lens, in 1757, has already been
referred to. In 1760 Dr. Black discovered that heat disappears, or becomes " latent,"
when ice is melted, or water evaporated. In 1761 several expeditions were sent out to
observe the transit of Venus which occurred in that year; for Halley in 1691 and again in
1716, had pointed out the way to find the sun's distance by observing transits of Venus.
About the year 1762 Bonnet and Spallauzani proved by a multitude of curious experiments
that many of the lower animals, such as worms, snails, newts, and lizards, can
grow new heads, tails, and limbs, if their first ones be cut off. In 1780 Lagrange
explained the peculiar motion of the moon known as libration\ his attention having been