The Locomotive - Lighthouse Survival Blog

18»;}.J THE LOCOMOTIVE. ^09
The Eig-hteenth Century.
"We are so accustomed to boast about the achievements of this wonderful Nineteenth
Century, that we are apt to look back at the eighteentli, its immediate predecessor, with
some little contempt. Many of us, indeed, are too apt to class it with the "dark ages,"
in which there was almost nothing done to improve our knowledge of things. In this
we err greatly; for during the eighteenth century there was great activity in the
scientific world, and in the workl of letters. Thus it was the age of Holiiigbroke,
AValpole, Swift, Defoe, Pope, Addison, Steele, Bishop Berkeley, Bishop Butler, Halley,
Bradley, Chatham, Frederick, Washington, Turgot, Clive, Hastings, Gibbon, Hume,
Adam Smith, Kant, Voltaire, Diderot, Rousseau, Richardson, Fielding, Sterne, Smollett,
Johnson, Goldsmith, Cowper, Gray, Reynolds, Gainsborough, Hogarth, Garrick, Cook,
Watt, Arkwright, Herschel, Black, Priestley, Franklin, Cavendish, Ilaudel, Bach,
Ilaydn, Mozart, Wesley, Whitefield, Pitt, Fox, Burke, Nelson, Bentham, Goethe, Burns,
Coleridge, Wordsworth, and Stevenson, as well as many others whose names are familiar
to us all. It also includes the French Revolution and the American War of Independence.
Let us see what the eighteenth century did for science. In the very earliest part of
it we have the researches of Sauveur, Bernouilli, Euler, and Lagrange on the musical
notes given out by stretched strings, and the laws governing the vibration of such strings.
In 1701 Boerhaave began his work at the university of Leyden, in Holland, and in a
short time he had laid the foundations of the science of organic chemistry. Others had
analyzed inorganic substances, and Boerhaave extended the methods of chemistry to
organic substances. In 1705 Newcomeu constructed his famous single-acting condensing
steam engine, which he used for pumping water. The valves were at first operated by
hand ; but it is related that a boy who was employed to work the engine devised aa
arrangement of strings by means of which the machine became self-acting. We cannot
vouch for the truth of this story. Indeed, it seems as though Newcomen, if skillful
enough to construct the engine, would have enough mechanical ingenuity to provide it
with self-working valves. In 1722 Graham discovered the daily variation of the compass
needle : that is, he found that the direction in which the needle i:)oints varies a little,
according to the time of day. This movement is very slight, and Graham deserves great
credit for detecting it. A few years later Bradley discovered what is known as the
aberration of light, and showed that the stars are not exactly in the places they appear to
be in, though they can never be more than 20 " away from their apparent places. He
rightly attributed this to the fact that the velocity of light is not infinitely greater than
the earth's orbital velocity. Bradley also discovered nutation, which is a slight oscilla-
tion of the earth's axis. It is not easy to give a popular explanation of either of these
phenomena, but they are of great importance to astronomy. About this time Dr. Hales,
an English chemist, made experiments on the quantity of water taken in by the roots
of plants, and given out by their leaves. He also discovered the way in which
plants breathe through the little stomata, or openings in their leaves, which were
discovered by Grew in 1670. In 1729 Chester More Hall discovered the very
important fact that it is possible to make a prism that will defect light, but which will
not decom2>ose it into colors. Newton, who died in 1727, believed this to be impossible;
but Hall showed how it could be done by using two pieces of glass, one of flint and the
other of crown. Nearly 30 years later (in 1757) DoUand took out a patent for lenses made
in this way. (He probably did not know of Hall's earlier discovery.) The great import-
ance of this discovery of achromatic lenses will be understood when one reflects that