158 W. R. Dawes on the Telescopic Appearances of Saturn. 
Art XIX.—On the Telescopic Appearances of pier: with a 
74-inch Telescope* ; by the Rev. W. R 
In the spring of last year (1854) I availed myself of an oppor- 
tunity of increasing the optical means in my possession, by t 
purchase of a 73-inch object-glass, having a focal length of nearly 
94 feet. It is the work of Mr. Alvan Clark, of Boston, U. S., 
who has long been known in that city as a most successful painter 
of portraits, but took to the manufacture of telescopes as an am- 
ateur. Being dissatisfied with reflectors, on which he commenced 
his operations, he attempted the mantifacture ae object-glasses ; 
and succeeded so well, that in the autumn o he communi- 
cated to me the places of some new and very ie double stars, 
which he had discovered with glasses whose apertures were 43 
and 54 inches. In the following year he completed an object- 
glass of 74 inches aperture for the observatory at Wiiliams Col- 
lege, which was tried at the Harvard Observatory by the Messrs. 
Bond, and highly approved ; immediately after which he com- 
mounted eae for his own use. At his requet I sent him 
some extremely difficult tests, selected from Mr. Otto Struve’s 
Pulkova Ca talogue ; several of which have a central distance of 
little more than half a second, and some even less. Yet of al 
these I soon received from the ingenious maker (who has also 
_ proved himself an acute observer) perfectly correct diagrams ; to- 
gether with the places of one or two extremely difficult new 
double stars which he had discovered with this glass. As a spe- 
cimen of these, 1 may mention 95 Ceti, which is at present fa- 
vorably situated for observation. Though unwilling to part with 
this glass, Mr. Clark consented to let me have it to try against my 
Munich telescope ; and in March, 1854, it arrived, with its tube, 
finder, and eye-piec 
“Though the crown glass has a considerable number of small 
bubbles, the performance of the telescope is not sensibly affected 
by that circumstance. In other respects the materials are good ; 
and the figure is so excellent, and so uniform throughout the 
whole of the area, that its power is quite equal to anything which 
_ an be expected of the aperture; and consequently, both in its 
_ illuminating and separating: power, it is decidedly superior to my 
old favorite of 63 inches aperture. As a specimen of its light, [ 
‘mention the companion of v Urse Majoris as having bee 
mensily seen with it; and also that I have never seen Sat- 
( tolerable circumstances during the present apparition 
Direct sate Enceladus, even when at or very near his con- 
* Extracted from the Monthly Ni of for 
tae Sass. ” pd eran gage en ipa 
