Volume 3 > Half-Volume 6

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greater distance. His discovery, and the proposal
of its use, excited much talk at the time, but unfor-
tunately nothing more, as it fell into neglect at home,
while it was adopted in France. In 1815 he was
interrupted by an application from the Edinburgh
town-council and Professor Playfair to take the place
of the latter in delivering the course of lectures on
natural philosophy. He complied; but finding that
such monotonous every-day occupation interrupted
him in his favourite studies, he did not long continue
in this intermediate change.
After he had improved upon the experiments of
Buffon in his attempts to discover the burning
mirrors of Archimedes, Dr. Brewster was to turn
those of Malus to a similar account. That French
savant, in a series of experiments conducted between
1808 and 1812, having improved on the original dis-
covery of Huygens by discovering the polarization of
light by reflection, Dr. Brewster commenced an
extensive series of experiments to ascertain the polar-
izing angle of a number of transmitting substances.
The authority upon which we chiefly rely thus follows
up the labours of the doctor on this head:�"He
pursued the subject of polarization in all its aspects,
and in all the conditions that modify it, in its rela-
tions with the nature and form of reflecting or re-
fracting bodies, in the geometrical, mathematical,
and trigonometrical relations of angles and planes
according to which it takes place; he established the
polarizing properties of a host of new substances;
he formulated general laws, completed and rectified
the discoveries made in the same region of study by
Fresnel, Arago, and Biot; profited by those dis-
coveries to make himself still further advances; and
by his own discoveries gave assistance to all the
researches which for a long time past have been, and
for a long time to come will be, made in the same
domain." While he followed out this field of dis-
covery which he made exclusively his own, Dr.
Brewster communicated the most important of its
results first in 1813, and afterwards in 1815, to the
Royal Society of London. The last of these was
a paper on the "Polarization of Light by Reflec-
tion;" and the society elected him a fellow, and
voted him their Copley medal for his discoveries
and researches. In the following year (1816) he
was honoured by the French Institute with half of
the prize of 3000 francs awarded for the two most
important discoveries made in Europe in physical
science during the two preceding years.
At this time also Dr. Brewster invented the kalei-
doscope. During the two previous years, while em-
ployed in his researches on the polarization of light,
his attention was drawn to certain effects of multipli-
cation produced by the use of reflecting plates of glass
placed at angles with each other; but being in pursuit
of a different result, he allowed the observation for
the present to rest. In 1816, however, while repeat-
ing the experiments of Biot on the action of fluids
on light, he made use of a trough composed of plates
of glass cemented at the angles, and was surprised
at the remarkable regularity of the form given by
reflection to some small irregular fragments of the
cement which had been forced through between the
plates. Struck by this phenomenon, he repeated
the experiment, first by fixing pieces of glass or other
small objects of irregular outline at the ends of the
reflectors, and then by making those objects movable
�and the result was the invention of the kaleido-
scope. Convinced of its importance in scientific
investigations on the subject of reflection, as well as
the inexhaustible aid which it would give to the
patterns of manufactures and other arts into which
design largely enters, Dr. Brewster patented the
instrument, and a number of them were made, one
of which was shown to the London opticians with a
view to their giving orders for it. The secret thus
revealed was a secret no longer; kaleidoscopes were
made by the thousand, in which scientific rule was
sacrificed to cheapness, and the instrument was soon
to be found not only in the hands of every man and
woman, but every schoolboy. In this way the patent
of Dr. Brewster was violated, the kaleidoscope de-
graded into a mere child's toy, and the great benefits
which it was to confer on science and manufactures
were never realized.
In 1818 or the following year Dr. Brewster was
honoured by the Royal Society of London with their
Rumford gold and silver medals. It was noticed
many years afterwards, that in announcing the death
of Faraday to the Royal Society of Edinburgh, he
mentioned that there was one person living who had,
like Faraday, taken all the medals of the Royal
Society of London�the Copley, Rumford, and
Royal medals. That "one," whose name he left
unmentioned, was himself. In 1819 he united him-
self with Professor Jameson in conducting the Edin-
burgh Philosophical Journal. Ten volumes of this
work having been already published, it was changed
in 1824 by the two editors into the Edinburgh
Journal of Science; and in sixteen volumes Dr.
Brewster published many interesting papers. During
this time he had made important investigations into
the mean temperature of the earth and the determi-
nation of isothermal lines, and also made various re-
searches in the mineral kingdom, which led to the
discovery of two new fluids and their properties.
In 1825 he was elected a corresponding member of
the French Institute. In 1827 he renewed the sub-
ject of the improvement in lighthouse illumination,
on which he had suggested improvements in 1813.
He now published his Account of a New System, &c.,
for the better illumination of lighthouses, and offered
his services for that purpose to the lighthouse boards
of Great Britain and Ireland. Nothing was done in
the matter, however, until 1833, when his method
was tested by public experiment. The places for
trial were the Calton Hill, Edinburgh, and Gullane
Hill, having between them a distance of twelve and
a half miles; and there the superiority of his "poly-
zonal lenses" was proved, for one of these with an
Argand burner of four concentric circles was found
to give a light equal to nine parabolic reflectors, each
carrying an Argand burner. The success of these
experiments was so effective that better modes were
introduced into the illumination of our lighthouses
over the whole United Kingdom.
The reputation of Dr. Brewster was now estab-
lished wherever natural science was understood and
valued, and the recognition was followed by the
increase of his personal influence and public honours.
In 1830 the Royal Society of London again honoured
him by the award of its royal medal for the researches
and discoveries by which the field of optical science
had been enlarged and its resources increased. In
union with Davy, Herschel, and Babbage, he origin-
ated the idea of a British Association for the promo-
tion of science by means of annual meetings, and the
first of these great intellectual parliaments, held at
York in 1831, was so successful that the institution
was established, and its anniversaries have since been
continued without interruption, and with a constantly
growing popularity. In the same year the decora-
tion of the Guelphine order of Hanover was con-
ferred on him, and in the following year he was
knighted by King William IV. In 1833 Sir David
Brewster was a candidate for the chair of natural
philosophy in the university of Edinburgh, but on