382 CAPTAIN W. DE W. ABNEY AND DR. T. E. THORPE ON PHOTOMETRIC 
of the corona in terms of its distance from the limb. We have, however, in the 
measures given, obtained results which will be of use in comparing the brightness of 
the corona on this occasion with that of other future eclipses; and we believe that 
measurements of the brightness obtained by the plan adopted, or by photography, 
will become a necessary observation in determinmg what connection, if any, the Sun¬ 
spot periods have with the coronal phenomena. 
We have to express our acknowledgments to Mr. H. A. Lawrance for the very 
ready and efficient aid which he rendered in mounting the equatorial, and in assisting 
in making the photometric measurements. 
To Captain Archer and his officers, Lieutenants Douglas and Bairnsfather, we 
are also greatly indebted for the lively and eminently practical interest which they 
manifested in the work of the expedition generally, and especially for their zealous 
co-operation in the particular observations which had been entrusted to us. Indeed, 
the entme crew of the “ Fantome” laboured in the most willing and cheerful manner, 
often under circumstances of considerable personal discomfort, to promote the success 
of the expedition in every possible way. 
Appendix. 
Observations made by Newcomb’s Method on the Visibility of Extension of the Coronal 
Streamers at Hog Iskmd, Grenada, by Commander Archer, R.N. 
1. A 9-inch disc was erected on a pole fastened to the N.W. corner of the observa¬ 
tory, much in the manner suggested in the instructions ; the distance of the eye-piece 
from a plumb-line hanging under the centre of the disc frame was exactly 40 feet. 
2. As a means of measuring the length of the streamers of the corona, I had fitted 
two copper circles concentric with the disc, supported on a light iron crqss; the 
diameter of the inner circle was disc diameter (13A inches), that of the outer one 
2 disc diameters (18 inches). 
3. In order to localise the position of the streamers, I decided to look upon the disc 
as a compass card, with the North point vertically upwards ; the arms of the iron 
cross therefore indicated the cardinal points. 
4. The iron crossbar which carried the eye-piece I had lengthened to 18 inches, in 
order to increase the limits of adjustment, and also to admit of the Sun being observed 
when at the proper altitude (18° 48') on several preceding days ; owing to this 
circumstance, I feel considerable confidence in the Sun’s having been nearly concentric 
with the disc at the beginning of totality, as on two previous days I timed the exact 
moment when the Sun’s centre was behind the centre of the disc, and found the 
calculated altitudes at the time were between 18° 48' and 18° 49', the calculated 
altitude at commencement of totality being 18° 47' 51". The position of the eye-piece 
was adjusted on the previous day, and required no further alteration. 
