SOLAR ECLIPSE MAY 6, 1883. 145 



Kensington, formerly assistant to Captain Abney, R. E. The instruments muler the charge of Mr. 

 Woons were not pointed directly to tlie sun but placed horizontally, the light being reflected to 

 them by a siderostat made by Cooke for the Royal Society, possessing a 12-iuch plane silver on 

 glass reflector. Four instruments were used in connection with it, and were arranged thus : 



1. An integrating spectroscope made by Hilger, with a long collimator of 3° angular aperture, 

 and 4i feet focus, with one large white glass prism and Dallmeyer lens of three-inch ajjcrture, 

 throwing an image on to a plate placed at a considerable angle by means of an extra swing back. 

 The instrument was adjusted with F in the center of the field, and the photographic plate was 

 moved regularly across the opening by means of clock-work. 



2. To the left of number one was placed a slit spectroscope for photographing the spectrum of 

 the corona, the image of the latter being projected on the slit. Two prisms and a camera of short 

 focus were used, only one plate being exposed throughout totality. This instrument is the same . 

 that was successfully used at Sohag last year, with this exception, that only one prism was used 

 on the previous occasion. 



3. To the right of number one was placed a prismatic camera with a lens of about 24 inches 

 focal length and about 2^ inch aperture, and a white glass prism of 00°. It was adjusted with F 

 in the center of the plate, as in Egypt, when a successful result was obtained from the blue to the 

 red end. 



4. On top of the three preceding instruments was placed a Rowland grating, which was 

 adjusted for parallel rays. Two cameras were attached to it, one of them taking in about 6° of 

 the first order, with F in the center of the field, and the other embracing about Qo of the second 

 order on the same side, with H in the center of the field. The result desired in this instrument 

 was the ring spectrum more widely dispersed than the jirismatic camera would give it. 



The integrating spectroscope gave a satisfactory result, photographing prominent lines in 

 the reversion spectrum at the beginning and end of totality. The slit spectroscope, for the corona, 

 was also very satisfactory, a good photograph of the coronal spectrum from the ultra violet to the 

 green being obtained. The spectrum was mainly continuous with a number of bright lines. Good 

 photographs were also obtained with the prismatic camera, but the faintness of the comparatively 

 few rings that were visible during this eclipse render the results less striking than the result 

 obtained in 1882. Bearing this in mind, no surprise will be occasioned at the failure of the Row- 

 land grating. Had such a series of rings appeared as were seen in 1882 a satisfactory result would 

 probably have been obtained. Mr. Lawrance had a 6-inch achromatic telescope, equatorially 

 mounted by Cooke of York, driven by clock-work. Attached to it was a Rutherford grating, 

 17,000 lines to the inch, mounted by Adam Hilger, of 1 Morniugtou Crescent, London, at a few 

 hours' notice. On each side of the grating was a camera, with lenses by Dallmeyee, one point- 

 ing to the first and the other to the second order. 



Clamped to this telescope was a 6-inch rapid rectilinear photographic lens, by Dallmeyer, of 

 about 4 feetjfocus. This lens was provided with a slit spectroscope, with a dense yellow-glass 

 prism, which gave a well-dispersed image on the camera screen. 



In each of these three cameras the F line was in the middle of the plate. 



All the cameras were made by Philip Meagher, and these three and the two used with the 

 Rowland grating were provided with an arrangement whereby the sensitive plate was moved by 

 a rack and pinion across the image of the spectrum, thus saving a great deal of time which would 

 otherwise have been lost in changing plates. 



Mr. Lawrance started taking photographs ten minutes before and continued doing so till ten 

 minutes after totality. He was successful in obtaining some of the bright lines before and after 

 S. Mis. 110 19 



