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clouds. One star of the third magnitude was clearly visible in 
the deep blue-gray surface inside the ring, which was free from 
any trace of vapour or cloud,—the other stars were lost in the 
moon’s light. ‘There was neither corona nor paraselene. 
“‘ The night was cold and frosty, the air dry and crisp, and 
pleasant to the feelings at the surface of the earth. The day 
had been remarkable fine and clear; the preceding night a 
clear one, with hard frost. 
‘« There was little or no wind stirring at 12 o’clock, night, 
10th-11th February. The barometer had been high for 
several days, and at 8 o’clock a. m. on the morning of the 
11th February was 30°52 inches ; thermometer on a northern 
exposure, 35° Fahr. 
‘¢The front of the house whence I looked is due south, 
the face ranging therefore E.and W. Looking out of window, 
and directly upwards. with my eye as nearly as possible plumb 
under the edge of the stone cornice about twelve feet above 
me, I perceived that the interior of the upper limb of the 
ring almost exactly reached the zenith, and formed a tangent 
to the line of cornice. 
«The moon’s place being known, therefore, it is easy to 
find the apparent diameter of the ring. 
H 
Thus let HH be the horizon; O the place of the observer ; 
Z the zenith ; M, moon’s place; ZR, apparent diameter of the 
halo. 
