TOTAL ‘SOLAH ECLIPSE OF JULY 18, 1860. 
341 
completely finished and ready for use. Since that time, every spare moment has been 
devoted to the final accomplishment of this work ; and, taking into account the inter- 
ruptions I am subject to, I feel convinced that it could not have been done in less time, 
although I candidly confess that the delay in sending in this Eeport must appear scarcely 
warranted. 
Determination of the Geographical Position, 
Previous to starting for Spain, I made certain preparations for facilitating the after- 
operations which I might have to carry out ; for I knew that the time allowed for get- 
ting the instruments into position would not be more than sutficient, even if each day 
permitted of observations being made. For this reason, I computed, with the formula 
sin (a + X) 
sin a 
(a= the polar distance, the colatitude). 
a series of star constants for all the stars likely to be visible in my instrument. I also 
computed a table of corrections, to be applied to the times of equal altitudes of the sun 
for intervals of two, three, four, five, and six hours, for each day from July 12 to July 
22 ; and similar corrections to the azimuths of equal altitudes, to enable me to lay otf 
at once a meridian line and erect a mark. My star constants did not, however, prove 
of much service ; for it was rarely that I could get a glimpse of the stars ; so that on only 
two occasions was I enabled to make any observations at all, and then only with the 
greatest difiiculty, although I watched patiently for opportunities through or between 
the clouds. 
I have already stated that I took vdth me three chronometers. My journeyman 
sidereal chronometer, Leplastrier 2915, is a very old one. In consequence of the wear 
of the fusee, this chronometer, which is an eight-day one, varies in its daily rate from 
8'6 seconds to 17 seconds, losing; but during long periods the rate is pretty uniform, as 
will be seen from the following observations ; — 
Leplastrier 2915. 
sec. 
From June 30 to July 3, losing daily 10-36 
From July 3 to July 30, losing daily 12-51 
From July 30 to August 7, losing daily 12-06 
From August 7 to August 17, losing daily 11-29 
On July 3, 21^ 24'", it was fast of Cranford sidereal time . . . 194-8 
Cranford observatory is west of Greenwich in longitude . . . 97-5 
Hence, on July 3, 21^ 24'", Leplastrier No. 2915 was fast of 
Greenwich sidereal time 97-3 
1^8 
On July 30, 6^ 30'", it was slow of Cranford sidereal time . . 138-0 
3 A 
MDCCCLXII. 
