250 
POPULAR SCIENCE REVIEW. 
at St. Petersburg, when the thermometer fell to 22° below zero of 
Fahrenheit’s scale. 
Babinet says, that every clergyman and every schoolmaster should be 
the possessor of a telescope, and occasionally give those under his care 
an idea of the inexhaustible riches of nature. It is only with that instru- 
ment that some of the above observations can be made ; and until the 
optical millennium arrives many will remain ignorant of the appearances 
of the sun, moon, and planets ; of the structure of the nebulae ; of the 
clusters and double stars. Some ingenious and inquisitive minds may 
wish, however, to construct an optic tube, through which some of the 
wonders of the heavens may be seen ; and a German astronomer of note 
recommends the following as a cheap non-achromatic comet-seeker : — 
For the object-glass, obtain a plano-convex of two and a half inches in 
diameter and thirty inches focus. The eye-glass is constructed of two 
lenses. That nearest the eye would be of an inch in diameter and two and 
a-half inches in focus ; and four inches from it, and between it and the 
object-glass, would be another of two inches in diameter and five inches in 
focus. The whole apparatus might be placed in a tin tube, blackened 
inside ; the two lenses composing the eye-piece to slide in a separate 
smaller tube. This will give a field of four or five degrees, and magnify 
about ten times, and will show the stars in the Pleiades and the sword- 
handle of Perseus very well. It is to be remembered that, in an achro- 
matic telescope, it is the object-glass which is the principal affair. Having- 
obtained that, the purchaser can have the tube, eye-pieces, and stand, fitted 
up at his discretion. But it must be confessed that much care should be 
used in buying an object-glass, as a bad one, with its twirling and distorted 
images, gives much more annoyance than pleasure to the purchaser ; and 
a good maker should accordingly be chosen for this most important part of 
the telescope.'"' 
Encke’s comet, after having been 390,000,000 of miles away from the 
sun, has returned to sight ; and on Feb. 6, of 1862, will only be 32,000,000 
of miles from that luminary. It may be seen with a small instrument, at 
the beginning of the year, by making use of a common star-map, with the 
lines of right ascension and declination marked as usual, on which the 
following places of the errant body are marked • 
Right Ascension. Declination. 
H. M. DEG. MIS'. 
Jan. 1 
22 
17 
3 
7 
North 
6 
22 
16 
2 
31 
33 
11 ...... . 
........ 22 
14 
1 
39 
?3 
16 
22 
9 
O 
19 
21 
22 
0 
1 
52 
South 
26 
21 
44 
5 
30 
31 
... 21 
17 
11 
1 
Feb. 5 
20 
47 
17 
23 
53 
* To those who do not wish to try the experiment of constructing a 
telescope at little or no cost, we recommend a small instrument made 
by Messrs. Parkes and Son, Birmingham, the cost of which is less than 
£ 4 . It is mounted upon a cast-iron stand, and sold in a convenient box. 
It has afforded us great pleasure — in enabling us to examine the more 
prominent objects in the heavens. There are doubtless other equally good 
and cheap instruments. 
