Intelligence and Miscellaneous Articles. 319 



nature of the corona reconciles itself so well with many facts that 

 have been difficult to explain, such as the low pressure at the sur- 

 face of the sun, that it gains thereby additional strength. 



The station occupied by my temporary observatory was Raw- 

 lins (latitude 41° 48' 50", longitude 2 h (T 44 s W. of Washington, 

 height 6732 feet above the sea), on the line of the Union Pacific 

 railroad, because, while it was near the central line of totality, it 

 had also the advantages of being supplied with water from the 

 granite of the Cherokee Mountain and of having a repair-shop 

 where mechanical work could be done. I knew by former experience 

 that the air there was dry and apt to be cloudless : in this parti- 

 cular our anticipations were more than fulfilled by the event ; for 

 the day of totality was almost without a cloud, and the dew-point 

 was more than 34° E. below the temperature. 



The instruments we took with us were as follows, and weighed 

 altogether almost a ton : — (1) An equatorial mounting with spring 

 governor driving-clock, loaned by Professor Pickering, Director of 

 Harvard Observatory. (2) A telescope of five and a quarter inches 

 aperture and seventy-eight inches focal length, furnished with a 

 lens specially corrected for photography, by Alvan Clark & Sons. 

 (3) A quadruple achromatic objective of six inches aperture and 

 twenty-one inches focal length, loaned by Messrs. E. and H. T. 

 Anthony, of New York ; to this lens was attached a E-utherfurd 

 diffraction grating nearly two inches square, ruled on speculum- 

 metal. The arrangement, with its plate-holders, etc., will be desig- 

 nated as a phototelespectroscope. (4) A four-inch achromatic 

 telescope with Merz direct-vision spectroscope, brought by Professor 

 Barker from the collection of the University of Pennsylvania. 

 (5) A four-inch achromatic telescope, also brought by Professor 

 Barker ; to it was attached Edison's tasimeter. Besides these there 

 were polariscopes, a grating spectroscope, an eye slitless spectro- 

 scope with two-inch telescope, and, finally, a full set of chemicals 

 for Anthony's lightning collodion process, which in my experience 

 is fully three times quicker than any other process. 



The arrangement of the phototelespectroscope requires further 

 description ; for success in the work it was intended to do, viz. 

 photographing the diffraction spectrum of the corona, was difficult, 

 and in the opinion of many of my friends impossible. In order to 

 have every chance of success, it is necessary to procure a lens of 

 large aperture and the shortest attainable focal length, and to have 

 a grating of the largest size adjusted in such a way as to utilize 

 the beam of light to the best advantage. Moreover the apparatus 

 must be mounted equatorially and driven by clockwork, so that the 

 exposure may last the whole time of totality ; and the photographic 

 work must be done by the most sensitive wet process. After some 

 experiments during the summer of 1877 and the spring of 1878, 

 the following form was adopted. 



The lens being of six inches aperture and twenty-one inches focal 

 length, gave an image of the sun less than one quarter of an inch 

 in diameter and of extreme brilliancy. Before the beam of light 



