B. 8. Holden—Light of Telescopes used as Night-glasses. 181 
7" 35", The tower disappears to the naked eye. In the finder 
the spire is still plamly seen, In the 15-inch, the whole of 
the spire, ribs, dome and many details well seen.— Hn. 
7" 42", The tower disappears to yh ar d eye. In the finder 
nd telescope everything still see ' 
8" 0™, 15-inch: the ribs on the dapat Me are gone.—Hn. and f. 
8" 7", Finder: the shape of the cupola is confused asi uncer- 
d 
8" 14", Finder: pretty muchsthe same. 15-inch: the spire on 
top of the cupola is still plain. No one looking with the 
miss 1t.—Hn. and 
8" 17", 15-inch: the spire on top of the cupola gone—Hn. I 
p. 
817, Finder: all shape to the cupola is gone.— Hn, 
8h ee ve inch: spire still seen by averted vision ; not well by 
8" 22™, he the tower is a mere black spot. 15-inch: spire 
is much fainter.— 
8° 23", 15-inch: the spire is gone, except that I can see that the 
outline of the cupola is not r — 
8" 25™. 15-inch: spire gene 8.” 
8 26". Finder: tower gone.—Hn. 
8° 27". Finder: tower and cupola gone.—/f. 
8° 27", 15-inch: tower and cupola gone.—Hn. 
8 29", 15-inch: tower has lost all shape.—/. ; 
8' 30", 15-inch: tower gone.—/f. 
rota i time mi sky was dark and the horizon Lapras 
clearer shown by small stars becoming visible the | 
finder, Probably the light Send above spoken of was snuipatad, 
8" 35", 15-inch: the cupola and tower can be plainly seen as a 
dusky cloud with a certain shape, when the telescope is vibra- 
nm. and fp. 
8° 37". 15-inch: pis 7 and 
8" 43", 15-inch: the cupola and tower are seen even better than 
before. The horizon is clearer. There is no difficulty in see- 
th them when the telescope is moved, and they can just be 
seen by direct vision.—/. 
8" 44", Same.—Hn. and f. 
8" 45", Stopped examination as there seemed to be no prospect 
of losing the tower as long as the horizon remained clear 
we had lost it we should have attributed the loss to haze at 
the horizon. Small stars 8-9 magnitude seen fr finder, 
They must have had an altitude of not more than 30’, 
It appears to me that this confirmation of Hersch $ experi- 
ments is important, and worth the attention of physicists. So 
far as I know there is no satisfactory explanation of the action 
of the ordinary eae seas, nor of the similar effect when 
large apertures are u 
Washburn Observatory, sane 1881, May 1, 
