DETEEMINATION OF DEFLECTION OF LIGHT BY THE SUN'S GRAVITATIONAL FIELD. 297 



Here we were met by Mr. JOHN NICOLAU, who had been instructed to assist us with 

 our baggage through to Sobral. We proceeded from Camocim to Sobral by train 

 on April 30, our baggage following the next day. 



We were met at Sobral station by representatives of both the Civil and Ecclesiastical 

 Authorities, headed respectively by Dr. JACOME D'OLIVEIRA, the Prefect, and Mgr. 

 FERREIRA, and conducted to the house which had been placed at our disposal by the 

 kindness of its owner, Col. VICENTE SABOYA, the Deputy for Sobral. We were joined 

 there nine days later by the Washington (Carnegie) Eclipse Commission, consisting 

 of Messrs. DANIEL WISE and ANDREW THOMSON. 



We are greatly indebted to Dr. LEOCADIO ARAUJO, of the State Ministry of Agri- 

 culture, who had been deputed to interpret for us and to assist us in our preparations. 

 His services were invaluable, and contributed greatly to our success, as also to our 

 well-being during our stay. 



10. A convenient site for the eclipse station offered itself just in front of the house ; 

 this was the race-course of the Jockey Club, and was provided with a covered grand 

 stand, which we found most convenient for unpacking and storage and in the pre- 

 paratory work. We laid down a meridian line, after which brick piers were constructed 

 for the ccelostats and for the steel tube of the astrographic telescope. Whilst this was 

 in progress the huts were being erected. 



The pier of the small ccelostat was constructed so as to leave a clear space in the 

 middle of one end for the fall of the weight, which was thus below the driving barrel 

 of the clock. By continuing the hole below the foundations of the pier, space was 

 provided for a fall of the weight permitting a run of 25 minutes. In the case of the 

 16-inch ccelostat, the clock was mounted on the top of a long wooden trunk, nearly 

 4 feet in length, which was placed on end, and sunk in the earth to a depth of about 

 2 feet. The weight descended inside the trunk directly from the driving barrel, and 

 had space for a continuous run of over half-an-hour. 



The 16-inch coelostat had free adjustment for all latitudes ; but the 8-inch one, 

 constructed for European latitudes, was mounted on a wooden base, inclined at an angle 

 of about 40 degrees, constructed before leaving Greenwich. The clock had to be 

 separated from the coelostat, mounted on a wooden base and reversed, to adjust to the 

 Southern Hemisphere. It performed very satisfactorily, and no elongation of the star 

 images is shown with 28 seconds' exposure. 



To provide for the changing declination of the sun the piers of the astrographic 

 telescope were made with grooves in the top, in which the wooden V-supports of the 

 tube could slide, thus allowing for the change of azimuth. 



The tube of the astrographic telescope was circular in section, and could rest in any 

 position in the Vs ; for convenience it was adjusted so that the directions of R.A. and 

 declination were parallel to the sides of the plate ; this involved a tilt of the plate 

 holders of about 4 degrees to the horizontal. 



The 4-inch lens was taken as an auxiliary ; we used the square wooden tube, 19 feet 



