., p. 259.

Physico-Mechanical Experiments on Various Subjects, London, 1709. This
contains descriptions of his various discoveries in electricity, many of
which are given in the Phil. Trans.

Hooee, Robert. See vol. ii., p. 215.

Micrographia, or Some Philosophical Descriptions of Some Minute Bodies,
London, 1665. An Attempt to Prove the Motion of the Earth, London, 1674.
Microscopical Observations, London, 1780. Most of Hooke's important
discoveries were contributed as papers to the Royal Society and are
available in the Phil. Trans.

Huygens, Christian (1629-1695). See vol. ii., p. 218.

Traite de la lumiere, Leyden, 1690. Complete works were published at
The Hague in 1888, under thetit le Ouvres completes, by the Societe
Hollandaise des Sciences. These books have not been translated into
English. Huygens's famous paper on the laws governing the collision of
elastic bodies appeared in the Phil. Trans, of the Royal Society for
1669.

Kepler, Johann. See vol. ii., p. 70.

Astronomia nova de motibus Stella Mortis, Leipzig, 1609, contains
Kepler's two first laws; and Harmonices mundi, 1619, contains the third
law, Phomomenon singulare, seu Mercurius in sole, Leipzig, 1609. Joannis
KepUri opera omnia, in 8 vols., Frankfort, 1858-1871.

Leeuwenhoek, Anthony van. See vol. ii., p. 179.

His discoveries are mostly recorded in the Phil. Trans. of the Royal
Society, between the years 1673 and 1723--one hundred and twelve papers
in all. His discovery of bacteria is recorded in Phil. Trans, for 1683;
and that of the discovery of the capillary circulation of the blood in
Phil. Trans, for 1790.

LiNNiEus, Carolus (1707-1778). See vol. ii., p. 299.

His Systema natures was published in 1735. Tro years later (1737)
he published Genera plantarum, which is generally considered as the
starting-point of modern botany. His published works amount to more than
one hundred and eighty.

Mariotte, Edme (died 1684). See vol. ii., p. 210.

Essais de physique (four essays), Paris, 1676-1679. 250

His De la nature de l'air, containing his statement of the law
connecting the volume and pressure of a gas, is contained in the second
essay.

Newton, Sir Isaac. See vol. ii., p. 241.

Philosophies naturalis principia mathematica, completed in July of
1687. The first edition was exhausted in a few months. There are several
translations, among others one by Andrew Motte, New York, 1848.

Paracelsus. See vol. ii., p. 159.

The Herme