468 
POPULAR SCIENCE REVIEW. 
This box, which should be made of black cloth or calico, fastened 
over a light framework of wire or cane, is to be placed in the 
sliding eye-tube as shown. The door b c enables the ob- 
server to “ change power" without removing the box, while 
larger doors d e and g f enable him to examine the image, — a 
dark cloth, such as photographers use, being employed, if 
necessary, to keep out extraneous light ; or the surface on 
which the image is received mav be formed of cut-glass or 
oiled tissue paper, in which case the image may be examined 
from without. 
Systematic observation of the sun, with a careful record of 
the number and position of the spots, of the arrangement of 
faculse, and of other phenomena visible with moderate powers, 
cannot fail to be highly valuable. In all drawings, lines of 
reference should be used, which, combined with the record of 
the time of observation, will render it easy to mark in at 
leisure the position of the sun's equator and visible pole. 
Careful notes should be taken of all appearances, even of those 
about which the observer may feel doubtful. The question 
whether some phenomenon, seen momentarily or for a short 
time only, has really taken place, will be settled if the pheno- 
menon happen to be observed simultaneously by another 
observer. Of such a nature, for instance, was the remarkable 
observation, simultaneously made by Messrs. Carrington and 
Hodgson, of a sudden flaming out of intense light on the 
solar surface. In such a case, evidence afforded by a small 
telescope may assume a high importance. 
Observation of Mercury and Yenus is rather difficult, owing 
to the intense light of these objects. Yenus, at her brightest, 
is visible to the naked eye in the daytime. She can be much 
better observed by day or by full twilight, than on a dark 
background ; and this not only from the fact that she is never 
visible on a dark background save at a low altitude, but because 
her great brilliancy is softened down when she is seen on a 
brighter background. 
For the observer who possesses only an alt-azimuth, or an 
equatorial without circles, it may be useful to note that Yenus 
or Jupiter (when favourably situated) by day, or Mercury 
when too near the sun to be easily detected by the naked eye, 
may readily be found in the following manner : — 
Across two uprights fasten a straight rod, so that, when looked 
at from some fixed point of view, the rod may correspond to 
the sun's path near the time of observation. The rod should 
also be at right angles to the line of sight to its centre. 
Fasten another rod at right angles to the first, and also at 
right angles to the line of sight just named. From the point 
of fastening, measure off and mark on the second rod equal 
