302 SIR F. W. DYSOX, PROF. A. S. EDDINGTON AND MR. C. DAVIDSON ON A 
Thermometer readings, July 10, 74°-4; July 13, 73°-7; July 14, 71°*9; July 16, 
72°'3; July 17, 72°-3. 
By July 18 we had obtained a sufficient number of reference photographs. Dis¬ 
mantling of the instruments was commenced, and the packing was completed on July 21. 
We left Sobral on July 22, leaving the packing cases in the hands of Messrs. Nicolau 
and Carneieo to be forwarded at the earliest opportunity, and arrived at Greenwich 
on August 25. 
The observers \vish to record their obligations to Mr. Chaeles Booth and the officers 
of the “ Booth ” Line for facilitating their journeys to and from their station at a 
difficult time. 
Photogeaphs Taken with the 4-inch Object Glass. 
16. These photographs were taken on 10 X 8-inch plates. By suitably mounting 
the camera it was made possible to obtain seven stars on the photographs, viz.. Nos. 2, 
3, 4, 5, 6, 10 and 11 of the table in § 5. Of the eight photographs taken during the 
eclipse seven gave measurable images of these stars, the other plate (No. 6) taken 
through cloud only showing a picture of the prominences. 
Plates of the same field taken under nearly similar conditions as regards altitude were 
taken on July 14, 15, 17 and 18 (civil date). Of these photographs, the second taken on 
July 14 with two exposures (referred to as 14^^ and 142j), two photographs taken on 
July 15 (referred to as 15i and 153 ), two on July 17 (17^ and 173 ), and the second 
photograph on July 18 (18.,) were measured for comparison with the eclipse plates. 
17. The micrometer at the Eoyal Observatory is not suitable for the direct com¬ 
parison of plates of tins size. It was therefore decided to measure each plate by 
placing, film to film upon it, another photograph of the same region reversed by being 
taken through the glass. A photograph for this purpose was taken on July 18. This 
plate is regarded merely as an intermediary between the eclipse plates and comparison 
plates and is referred to as the scale plate, being used simply as a scale providing 
points of reference. In all cases measurement was made through the glass of the 
scale plate, adjusted on the eclipse or comparison plate which was being measured, so 
that the separation of the images on the two plates did not exceed one-third of a 
imllimetre. The plates were held together by clips which ensured contact over the 
whole surface. This method of measurement was found to be very convenient. Each 
plate was measured in two positions, being reversed through 180 degrees, and the accord¬ 
ance of the result showed that the method of measurement was entirely satisfactory. 
The measures, both direct and reversed, were made by two measurers (Mr. Davidson 
and Mr. .Fuenee), and the means taken. There was no sensible difference between 
the measurers, which is satisfactory, as it affords evidence of the similarity of the images 
on the eclipse and comparison and scale plates. 
The value of the micrometer screws (both in R.A. and Deck) is 6"-25. 
18. The results of the measures are as follows :— 
