56 Capt. E. H. Hills and Mr. H. F. Newall. 



X 4233 would be the best available for the determination of displace- 

 ment dne to velocity. 



The linear dispersion in the photographed spectrum is about 15 

 tenthmetres per millimetre at H 7 . The relation between the velocity 

 in the line of sight and one complete revolution of the micrometer to 

 be used in the measuring the plate is about 260 kilometres per second 

 for one revolution. 



The scale of the photograph is such that one degree on the sky 

 corresponds to about 9 mm. on the plate. 



The effective aperture of the combination regarded as an instru- 

 ment for producing monochromatic images of a slit-shaped region of 

 the corona is T V. 



The adjustment of the axis of the instrument to parallelism with 

 the earth's axis, was accomplished in the same manner as that adopted 

 for adjusting the ccelostat. A theodolite with decimation circle was 

 attached to a part of the frame of the spectroscope, specially prepared 

 for it, between the camera and the collimator. The adjustment was 

 very easily and satisfactorily made : in altitude by observations made 

 with the spirit level attached to the theodolite-telescope, and in 

 azimuth by observations of the sun made some hours before or after 

 noon. 



Programme of Exposures and General Results. 



I. Spectra of the Corona. A set of five photographs, from which 

 the relative velocity in the line of sight of the eastern and western 

 equatorial regions of the corona could be deduced, was to be taken 

 with the spectroscope with two slits. 



The programme of exposures was carried out completely successfully, 

 as follows : 



Thirty minutes before totality, plate A was exposed for 15 seconds 



for spectra of sunlight diffused from the sky near the sun. 

 Fifteen minutes before totality, plate B was exposed for 20 seconds 



for a duplicate of plate A taken in falling temperature. 

 During totality, plate No. 1 was exposed for 100 seconds for the 



spectra of the eastern and western regions of the corona. 

 Fifteen minutes after totality, plate C was exposed for 15 seconds 



for spectra of sunlight diffused from the sky near the sun. 

 Thirty minutes after totality, plate D was exposed for 15 seconds for 



a duplicate of plate C under different temperature conditions. 



Result. On development, the photographic plate No. 1 showed no 

 trace of any impress of the coronal spectra, though the development 

 was pressed as far as possible. 



It is clear that the failure is due to the f aintness of the corona in 

 the region photographed. Captain Hills was successful in photo- 



