SPECTROSCOPIC OBSERVATIONS. 65 



compaiv the form of the corona as seen as a whole with its form 

 as seen on one of the lines of the spectrum say " 1474 K," or 

 in other words to compare the corona itself with the distribution 

 in it of a certain gas. such as " coronium." 



MR. J. EVERSHED'S REPORT. 



THE work which I undertook at the recent eclipse was similar 

 to that which I had intended to do in Norway in 1896, but 

 was on a rather more extended scale. It consisted in obtaining 

 spectrum photographs of the corona, prominences, and the 

 reversing layer or Hash spectrum. 



On the former occasion I hoped to secure these photographs 

 with one instrument only a prismatic camera of 2 in. aperture 

 and 36 in. focus (described in the Memoirs of this Association, 

 voL vi., part 1) ; but for the Indian eclipse I had, in addition 

 to this instrument, a slit spectrograph containing two quartz 

 prisms, intended for a single exposure on the corona during 

 the whole of totality ; and a large slitless spectrograph attached 

 to a 6-in. telescope for photographing the flash spectrum on a 

 larger scale than was possible with the prismatic camera. 



Besides the three photographic instruments, I had available 

 a 4 in. polar heliostat lent by Mr. Maw, and a 3-in. equatorial 

 telescope, with solar spectroscope attached, for making visual 

 observations on the bright lines, and to determine the exact 

 moment when to expose the prismatic camera and large spectro- 

 graph in order to photograph the flash spectrum. 



The heliostat was used to supply light to the prismatic 

 camera and to the slit spectrograph. It was of the ordinary 

 form, with two mirrors, but was modified for the special work 

 by removing the second mirror and mounting it in the same 

 plane as the first, so that two beams of light were available 

 instead of one beam twice reflected. 



Thanks to the facilities afforded us by the Indian Government 

 in providing workmen and materials, and to the very attentive 

 way in which all our needs were provided for by the Assistant 

 Commissioner, Mr. D. 0. Morris, Lieut. R.A., I was able to get 

 all these instruments erected and in working order in time for 

 the eclipse, although from the day of our arrival at Talni we 

 had only a fortnight in which to make our preparations. 



In setting up the instruments and in putting together the 

 large spectrograph and 6-in. telescope I had also the advantage 

 of receiving most efficient help from Captain P. B. Molesworth, 

 R.E., without whose skilled assistance it would have been im- 

 possible to get all ready in time. 



My observing hut was similar to those built for the other 

 members of our party, the frame consisting of four uprights 



5 



