Light Sjiots in the Lunar Night. 53 



review of some of the neglected and perhaps undervalued 

 speculations of Schroter. 



However, we must now see what happened to this astrono- 

 mer, 1788, Sept. 26, 4h. 25m. in the early morning, when he 

 often rose to carry on his investigations, in the spirit of old 

 Hevel's resolution, " As far as I am concerned, I will not 

 suffer sleep to be so dear to me, that the investigation of so 

 great a matter should not be dearer. 33 It was 3^ days before 

 the new moon : the sky was so clear that the streaks of Tycho 

 were distinctly visible in the dark side : and with a fine 7- foot 

 Newtonian made by Herschel, and a power of 161, he examined 

 the region of Proclus (12), as the second point in reflective 

 power on the moon. Notwithstanding however its favourable 

 position on the hemisphere, and its intensity in the full moon, 

 he could not find a trace of it. The most probable explanation 

 of this failure — the minute breadth of the ring, which is the 

 only reflective part* — did not occur to him, and he was pro- 

 ceeding to scrutinize the neighbourhood of the N. limb, when 

 he was struck all at once by the appearance of a small whitish 

 spot of somewhat misty light, about 4" or 5" in diameter, like 

 a star of the 5th mag. seen with the naked eye, which, had a 

 faintish radiating glimmer around it, and on a small scale 

 looked much like the spot Kepler (41) as viewed on the 

 enlightened side with a moderate power. To preclude any 

 deception, he traversed several times the rest of the unenlight- 

 ened disc, and recognized its features, as before, with much 

 distinctness, but as soon as ever this N. part was brought into 

 the field, again repeatedly found the same luminous spot, 

 sometimes brighter, at others more faint, but always distinct, 

 and in an unvaried position. Previous to an intended measure- 

 ment with his projection machinef 

 he estimated its place to be very 

 near the edge of the dark Mare 

 Imhriurrij and about 1J to 14- 

 diameter, or V 16" to V 20" 

 distant from a dark spot which 

 he at once recognized as Plato. 



This estimation he repeated 

 and confirmed several times while 

 he kept constantly under review the other features of the dark 

 disc. But now his spot was becoming at intervals indistinct — 

 then uncertain — and soon after totally disappeared. To obtain 



* See Intellectual Observer, vii. 258. 



f This was a simple measuring apparatus always used by him in selenography, 

 and consisting of a board covered with white paper ruled in squares, and placed 

 at a suitable distance, which was viewed with one eye, while the lunar surface 

 was looked at with the other. A modification with circular discs, for measuring 

 planets, has been already described. Intellectual Observer, viii. 458. 



