2 MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 



The investigations of Gauss and otliers for the telescope, and of 

 Helmholtz and others in the optics of the eye, have taught us the 

 imperfections of both these optical instruments. Newton's suggestion 

 of 1717 has been carried out, in one form or another, by Bond (1851), 

 Lassell (1852), Piazzi-Smyth (1856), and others, and has resulted in 

 the foundation of mountain observatories like those of Mount Hamil- 

 ton, Etna, Nice, etc. Galileo's tower at Arcetri is the forerunner of 

 the magnificent establishments of modern times. The greatest tele- 

 scopes of the world are but consequences of his "optick tube." 



In the paragraphs which immediately follow I have brought together 

 short accounts of the principal steps in the evolution of the idea of the 

 modern observatory and its requirements. The succeeding chapters 

 will treat the more important of these in still greater detail. 



Frangois de Plantade, an astronomer and geodesist of Montpellier 

 {b. 1670, d. 1741), a colleague of Cassini, first proposed an astronomi- 

 cal observatory on the Pic-du-Midi, (9439 feet), and made several 

 ascents with that end in view. He died, in fact, on the mountain 

 while engaged in observations. The noted Chevalier D'Angos, it is 

 said, made a series of astronomical observations at this station. In 

 1860 (July 18) a solar eclipse was photographed from the summit. It 

 is worthy of note that the altitude of the station is the same as that 

 of Quito, Ecuador. 



In 1821-2-3 Sir John Herschel and Sir James South re-observed 

 a number of Sir William Herschel's double-stars at Sir James 

 South's London observatory. Finding that the conditions existing 

 there were not satisfactory. Sir James South, in 1824, transported his 

 largest telescope (aperture 5 inches) to Passy, in France, where the 

 work was continued. This was, I believe, the first astronomical expedi- ■ 

 tion in search of improved conditions. It was, however, entirely i 

 unnecessary to move a 5-inch telescope out of England in search of ti 

 a climate. The southern counties, Sussex, etc., would have provided 

 good observing stations. 



In various works, Alexander Yon Humboldt called attention to .^| 

 the steadiness of the stars in the tropics, where the distribution of tem- 

 perature is more regular than in our temperate regions. On the 

 rainless deserts of Peru the stars generally cease to twinkle at an i 

 altitude of 10° to 12°. In Arabia, India, and on the shores of the j 

 Persian Gulf similar conditions are said to prevail. 



In the year 1851 a total solar eclipse occurred in Norway. The 

 corona was observed by Professor G. P. Bond, Director of Harvard ^ 

 College Observatory, among others. Before leaving Norway, Bond ' 

 determined to search for the corona by occulting the sun in full day- f 

 light, selecting some high station with an atmosphere free from dufiti 



