SUMMARY OF THE CONTENTS. XVll 



nniverse prepared the way for these disccveries. Nicholas Copernicus 

 was engaged in making observations with the astronomer Brudzewski 

 at Cracow when Columbus discovered America. Ideal connection be- 

 tween the sixteenth and seventeenth centuries, by Peurbach and Re- 

 giomontanus. Copernicus never advanced his system of the universe 

 as an hypothesis, but as incontrovertible truth — p. 301-313. Kepler 

 and the empirical planetary laws which he discovered — p. 313-317. 

 Invention of the telescope; Hans Lippershey, Jacob Adriaansz (Meti- 

 as), and Zacharias Jansen. The first fruits of telescopic vision : mount- 

 ains of the moon ; clusters of stars and the Milky Way ; the four satel- 

 lites of Jupiter ; the triple configuration of Saturn ; the crescent foma 

 of Venus; solar spots; and the period of rotation of the sun. The dis- 

 covery of the small system of Jupiter indicates a memorable epoch in 

 the fate and sound foundation of astronomy. The discovery of Jupiter'a 

 satellites gave rise to the discovery of the velocity of light, and the rec- 

 ognition of this velocity led to an explanation of the aberration-ellipse 

 of the fixed stars — the perceptive evidence of the translatory movement 

 of the earth. To the discoveries of Galileo, Simon Marius, and Johann 

 Fabi-icius 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 — p. 317-331. 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 

 refraction and polarization ; 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 with- 

 out 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 observations 

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

 Torricellian tubes, and measurements of altitude by the position of the 

 mercury in them. ' Knowledge of atrial currents, and the influence of 

 the earth's rotation on them. Law of rotation of the winds conjectured 

 by Bacon. Happy, but short-lived, influence of the Accademia del Ci- 

 mento on the establishment of mathematical natural philosophy, as based 

 on experiment. Attempts to measure the humidity of the atmosphere ; 

 condensation hygrometer. The electric process; telluric electricity; 

 Otto von Guericke sees, for the first time, light in induced electricity. 

 Beginnings of pneumatic chemistry ; observed increase of weight in 

 metals from oxydation ; Cardanus and Jean Rey, Hooke and Mayow. 

 Ideas on the fundamental part of the atmosphere {spiritus nitro-aSreus), 

 which enters into all metallic calxes, and is necessary to all the processes 

 of combustion, and the respiration of animals. Influence 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 mathemat- 

 ical figure of the earth — we see perceptibly reflected all the conditions 

 of a primitive age, or, in other words, the primitive fluid state of the 

 rotating mass and its consolidation into a terrestrial spheroid. Meas' 



