VELOPMENT OF ASTRONOMY. 



Bv \\'. ALFKKl) PARR 



Instrumental. 



The instruments known to the Ancients ic.g.. The Gnomon. .\rmii;.larv Sphere. 



.■\STROLABE, QUADRANT and SextaN'T) continue in use. 

 Bernard Walther Id. 1504) introduces the use of Clocks in astronomical observations. 



Tycho equips his Obserwatory L'kaniborg with greatly-enlarged and accurately- 

 divided Quadrants and Sextants, and invents the method of sub-di\iding the 

 degrees on the arc of an instrument by transversals. 



Hans Lippcrslicy invents the Refracting Telescope in 1608. and Gir/)7c'o, construct- 

 ing one in 1609 for himself, magnifying thirty-two times, applies the instrument to 

 Astronomv, while Kepler improves it in theory. 



Heveliiis is the last to make observations without Telescopic Sights, but Gascoigitc 

 invents the t'lLAR Micrometer about 1640, and Picard definitely inaugurates the 

 adoption of the Telescope in Conjunction with the Quadrant. 



Htiygeiis adapts the Pendulum to Astronomical Clocks in 1656. and invents the 

 Compound Eyepiece, while both he and Hevelius improve definition by employing 

 Tubeless ("Aerial") Refractors over one hundred feet long. 



Gregory proposes a form of Reflecting Telescope in 1663. but Neicton constructs 

 the first in 1668. 



Rociner invents the Transit Instrument and Eouatorial, about 1690. 



Paris Observatory erected 1671 ; Greenwich Observatory, 1675. 



Griilii/iii. lUrd. Cory and Raiusdcii 

 Quadrants about this period. 



the most celebrated constructors of Mural 



Dolloiid in\ents the Achromatic Refractor, 1758 (suggested by Hull, 17331. 

 Giiiiiand improves the manufacture of Optical Glass, 1799, enabling Fntiuiiliutcr to 



construct Large Refractors. 

 Win. Herschel advances the construction of Reflectors and erects his Forty-Foot 



Telescope in 1789. 



Frauenhofer applies the Spectroscope to Astronomy 1815, adapts Clock-work 

 Motion to refractors 1824, and erects the First Heliometer 1829. 



Reiehenbach. Repsold and Troughtun effect Improvements in Instrument-making 

 early in this century. 



Lord Ross erects his great Six-Foot Reflector at Parsonstown, 1845. 



The first regular observatories of the S. Hemisphere (Paramatta. 1821 ; Cape. 1829) arc 

 founded. 



The first regular application of Photography to Astronomy is made with the Keu- 

 Photoheliograph in 1859, but the greatest advances are made after the adoption 

 by Muggins in 1876, of the Gelatine Dry Plate. 



The Astro-Physical Observatories of Potsdam and Meudon, founded 1874 and 1886. 



The First Great Refractor {Neicall. twenty-five inches), erected 1870: Lick, 

 Thirty-Six Inches, 1888; Yerkes, Forty i'nchics, 1897. 



The Equatorial Coude erected at Paris, 1882. 



Chandler introduces the Almucantar in 1884. ; 



Hale devises the Spectroheliograph in 1889. 



Turner introduces in 1895 the Coelostat, being a modification of the Siderostat. 



The Mount Wilson Solar Observ.atory is established in 1905, and equipped with 

 horizontal and vertical Coelostat Telescopes, Spectrographs, and Spectro- 

 heliogkaphs, besides the Chemical and Physical Apparatus of the 

 Laboratory. 



General. 



DiuMug this ccnturx- .\stronomy is 

 still under the Influence of 

 Greek Tradition, and is at 

 first solely Geometrical, 

 treating of the motions of the 

 heavenlv bodies. 



Rise of the Dynamic Conception 

 in .Astronomy, which after 

 Galileo is Physical, and 

 afteriVctc-^o;; Gra\ttational, 

 treating of the appearance 

 and nuitual attraction of the 

 hea\'enly bodies. 



Rise of Descriptive Astronomy 

 and CoSMOGON^■ with Wni. 

 Ucrsehel and Laplaee. 



Rise of Chemical .\stronomy, 

 after Frauenhofer, treating of 

 the composition of the heavenlj' 

 bodies. Astronomy now 

 gradually widens its sphere 

 and establishes a UNIFICATION 

 OF THE Sciences, by extend- 

 ing terrestrial and planetary 

 gravitation to stellar systems, 

 and by showing the essential 

 identity of cosmical matter 

 throughout the visible universe. 



