Barker.] »OU [Nov. L5, 



Bpectroscope, 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 farther descrip- 

 tion, 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 attain- 

 able 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 experi- 

 ments during the. summer of 1877 and the spring of 1878, the following 

 form w T as 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 dia- 

 meter and of extreme brilliancy. Before the beam of light from the lens 

 reached a focus it was intercepted by the Rutherford grating set at an angle 

 of sixty degrees. This threw the beam on one side and produced there 

 three images — a central one of the sun and on either side of it a spectrum ; 

 these were received on three separate sensitive plates. One of these 

 spectra was dispersed twice as much as the other, that is, gave a photo- 

 graph twice as long. This last photograph was actually about two inches 

 long in the actinic region. If, now, the light of the corona was from in- 

 candescent gas giving bright lines which lay in the actinic region of the 

 spectrum, I should have procured ring-shaped images, one ring for each 

 bright line. On the other hand, if the light of the corona arose from in- 

 candescent solid or liquid bodies, or was reflected light from the sun I was 

 certain to obtain a long band in my photograph answering to the actinic 

 region of the spectrum. If the light was partly from gas and partly from 

 reflected sunlight a result partly of rings and partly a band would have 

 appeared. 



"Immediately after the totality was over and on developing the photo- 

 graphs, I found that the spectrum photographs were continuous bands 

 without the least trace of a ring. I was not surprised at this result, be- 

 cause during the totality I had the opportunity of studying the corona 

 through a telescope arranged substantially in the same way as the photo- 

 telespectroscope and saw no sign of a ring. 



"The plain photograph of the corona taken with my large equatorial on 

 this occasion shows that the corona is not arranged centrally with regard 

 to the sun. The great mass of the matter lies in the plane of the ecliptic 

 but not equally distributed. To the eye it extended about a degree and a 

 half from the sun toward the west, while it was scarcely a degree in length 

 toward the east. The mass of meteors, if such be the construction of the 

 corona, is therefore probably arranged in elliptical form round the sun. 



"The general conclusion that follows from these results is that on 



