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SIR XORMAX LOCKYER AYD OTHERS OX THE 
each more powerful than any previously used. One of them had an aperture 
of 6 inches, and a focal length of 90 inches, with two prisms of 45° each ; the 
other had an aperture of 9 inches, and a focal length of 120 inches, with one prism 
of 45°. Both were fixed, and sunlight was reflected into them hy siderostats. 
The G-inch instrument was placed in a horizontal position, hut the 9-inch was set 
up at such an angle that the direction of the moon’s motion across the sun was 
coincident with the direction of dispersion. 
To obtain this result in the case of the 9-inch instrument, the position of the 
telescope was previously carefully calculated by Dr. Lockyee, and it was found that to 
gain the desired object, the tube had to be deviated 28° to the east side of the meridian, 
depressed at the object glass end 24° 40', and twisted about its optical axis 41° in 
the opposite direction to the hands of a watch. To secure this accurate position at 
the eclipse camp, suitable packing cases were chosen and special wooden tops were 
made, the whole being erected at Kensington previous to its departure for India. 
For the information of future observers, the following diagram (fig. G), is given 
showing a perspective view of the method of supporting the square tube. 
Fig. 6. Illustrating position of 9-inoh prismatic camera. 
