721 
of Edinburgh, Session 1881 - 82 . 
The moon’s place is given in the Almanac to the tenth part of a 
second of arc, which distance is passed over in about one-fifth part 
of a second of time. Now with a telescope of moderate power, say 
50, we are able to note the instant of contact to within a second ; 
and hence, in order to get the full advantage of our comparison, the 
calculations must be made at least to the nearest second. 
The elements of the eclipse are only useful for a preliminary 
determination sufficiently near to give the limits within which the 
strict calculations must extend ; and the local times given for our 
principal observatories are only to tenths of a minute ; hence it is 
that a working astronomer, even though he be at one of these 
observatories, must find means for a more minute determina- 
tion ; while we who are elsewhere placed must, of necessity, 
make the calculation for ourselves. The impossibility of having 
the details so given in the Almanac as to suit every observer, is 
obvious. 
The accompanying six figures show the appearance which the 
sun will have, as seen from Edinburgh, at intervals of ten minutes 
from 6 h 30 m till 7 h 20 m on the morning of Wednesday the 17th; 
and the times of the principal phases, civil reckoning, are 
First Contact at 6 h 25 m 56 s 
Greatest Phase at 6 52 58 
Last Contact at 7 20 53 
At the middle of the eclipse 200" of the sun’s diameter will be 
covered. 
I have followed a method of computation differing somewhat 
from that usually adopted. It makes a considerable part of the 
work useful for all places, and avoids approximative formulse. 
The data given in the Almanac make it a very easy matter to 
decide on the limits within which the special calculations are to be 
made. In the present instance the times were taken at intervals of 
ten minutes from 18 20 m till 19 h 30 m Greenwich time. 
The first step was to interpolate the sun’s and moon’s geocentric 
places, and to compute the moon’s co-ordinates in relation to the 
earth’s equator, to the meridian of a known observatory (Edinburgh), 
and to a plane perpendicular to these two. Eor this part of the work, 
