[XX] COSMOS. 



Copernicus never advanced his system of the universe as an hypothesis, 

 but as incontrovertible truth pp. 681-694. Kepler and the empirical 

 planetary laws which he discovered pp. 694-699. Invention of the 

 telescope ; Hans Lippershey, Jacob Adriaansz (Metius), and Zacharias 

 Jansen. The first fruits of telescopic vision : mountains of the moon : 

 clusters of stars and the milky way ; the four satellites of Jupiter ; the 

 triple configuration of Saturn ; the crescent form of Venus ; solar spots; 

 and the period of rotation of the sun. The discovery of the small system 

 of Jupiter indicates a memorable epoch in the fate and sound foundation 

 of astronomy. The discovery of Jupiter's satellites gave rise to the 

 discovery of the velocity of light, and the recognition of this velocity led 

 to an explanation of the abberration-ellipse of the fixed stars the 

 perceptive evidence of the translatory movement of the earth. To the 

 discoveries of Galileo, Simon Marius, and Johann Fabricius, followed 

 the discovery of Saturn's satellites by Huygens and Cassini, of the 

 zodiacal light as a revolving isolated nebulous ring by Childrey, of the 

 variation in brilliancy of the light of the fixed stars by David Fabricius, 

 Johann Bayer, and Holwarda. A nebula devoid of stars in Andromeda 

 described by Simon Marius pp. 699-714. While the seventeenth 

 century owed at its commencement its main brilliancy to the sudden 

 extension of the knowledge of the regions of space afforded by Galileo 

 and Kepler, and at its close to the advance made in pure mathematical 

 science by Newton and Leibnitz, the most important of the physical 

 problems of the processes of light, heat and magnetism, likewise 

 experienced a beneficial progress during this great age. Double refrac- 

 tion and polarisation; traces of the knowledge of the interference of 

 light in Grimaldi and Hooke. William Gilbert separates magnetism 

 from electricity. Knowledge of the periodical advance of lines without 

 variation. Halley's early conjecture that the polar light (the phos- 

 phorescence of the earth) is a magnetic phenomenon. Galileo's ther- 

 moscope and its employment for a series of regular diurnal observa- 

 tions at stations of different elevation. Researches into the radiation of 

 heat. Toricellian tubes and measurements of altitude by the position of 

 the mercury in them. Knowledge of aerial currents and the influence 

 of the earth's rotation on them. Law of rotation of the winds con- 

 jectured by Bacon. Happy but short-lived influence of the Academica 

 del Cimento on the establishment of mathematical natural philosophy as 

 based on experiment. Attempts to measure the humidity of the atmos- 

 phere ; condensation hygrometer. The electric process; telluric elec- 

 tricity ; Otto von Guerike sees, for the first time, light in induced elec- 

 tricity. Beginnings of pneumatic chemistry; observed increase of 

 weight in metals from oxidation; Cardanus and Jean Rey, Hooka and 

 Mayow. Ideas on the fundamental part of the atmosphere (spiritm 

 nitro-aereus) which enters into all metallic calxes, and is necessary to 

 all the processes of combustion, and the respiration of animals. Influ- 

 ence of physical and chemical knowledge on the development of geognosy 

 (Nicolaus Steno, Scilla, Lister) ; the elevation of the sea's bottom and of 

 littoral districts. In the greatest of all geognostic phenomena the 

 mathematical figure of the earth we see perceptibly reflected all the 



