E. 8. Holden—LTrght of Telescopes used as Night-glasses. 129 
It may not be out of place to add an extract from an article 
published in the Philosophical Magazine by Stokes in 1846. 
“ All these results would follow immediately from the theory 
of aberration which I proposed in the July number of this 
magazine: nor have I been able to obtain any result admitting 
of being compared with experiment, which would be different 
according to which theory we adopted. This affords a curious 
instance of two totally different theories running parallel to 
each other in the explanation of phenomena. I do not sup- 
pose that many would be disposed to maintain Fresnel’s theory, 
when it is shown that it may be dispensed with, inasmuch as 
we would not be disposed to believe, without good evidence, 
decisive experiment.” 
n conclusion, I take this opportunity to thank Mr. A. Gra- 
ham Bell, who has provided the means for carrying out this 
work, and Professor Vogel, the Director of the Astrophysi- 
calisches Observatorium, for his courtesy in placing the re- 
sources of his laboratory at my disposal. 
Art, XXII.— Observations on the Light of Telescopes used us 
Night- Glasses ; by Epwarp 8. Honpen. ‘ 
In the Philosophical Transactions for 1800, vol. xe, p. 67, 
Sir William Herschel says: “In the year 1776, when I had 
erected a telescope of 20 feet focal length, of the Newtonian 
construction, one of its effects by trial was that when toward 
evening, on account of darkness, the natural eye could not pen- 
etrate far into space, the telescope possessed that power suffi- 
ciently to show, by the dial of a distant church steeple, what 
o'clock it was, notwithstanding the naked eye coald no longer 
see the steeple itself. Here I only speak of the penetrating 
power, for though it might require magnifying power to see the 
figures on the dial, it could require none to see the steeple.” 
I had long been desirous of trying this experiment with a 
large aperture, and made several attempts in 1874 to have the 
Dome of the 26 inch Clark refractor at Washington so arranged 
that a terrestrial object could be seen, but without success. I 
therefore took the first opportunity to try the effect of a tele- 
scope under these conditions at the Washburn Observatory, 
where the large equatorial commands the horizon. The most 
suitable object for examination was the tower of the Hospital 
