the
observer to judge whether the screen is properly situated in the last
respect.

We wish now to direct the tube towards the sun, and this "without
dazzling the eyes as by the ordinary method." This may be done in two
ways. We may either, before commencing work--that is, before fastening
our elastic cord so as to exclude all light--direct the tube so that its
shadow shall be a perfect circle (when of course it is truly directed),
then fasten the cord and afterwards we can easily keep the sun in the
field by slightly shifting the tube as occasion requires. Or (if the
elastic cord has already been fastened) we may remove the eye-tube and
shift the telescope-tube about--the direction in which the sun lies
being roughly known--until we see the spot of light received down the
telescope's axis grow brighter and brighter and finally become a _spot
of sun-light_. If a card be held near the focus of the telescope there
will be seen in fact an image of the sun. The telescope being now
properly directed, the eye-tube may be slipped in again, and the sun may
be kept in the field as before.

There will now be seen upon the screen a picture of the sun very
brilliant and pleasing, but perhaps a little out of focus. The focusing
should therefore next be attended to, the increase of clearness in the
image being the test of approach to the true focus. And again, it will
be well to try the effect of slight changes of distance between the
screen and the telescope's eye-piece. Mr. Howlett considers one yard as
a convenient distance for producing an excellent effect with almost any
eye-piece that the state of the atmosphere will admit of. Of course, the
image becomes more sharply defined if we bring the screen nearer to the
telescope, while all the details are enlarged when we move the screen
away. The enlargement has no limits save those depending on the amount
of light in the image. But, of course, the observer must not expect
enlargement to bring with it a view of new details, after a certain
magnitude of image has been attained. Still there is something
instructive, I think, in occasionally getting a very magnified view of
some remarkable spot. I have often looked with enhanced feelings of awe
and wonder on the gigantic image of a solar spot thrown by means of the
diagonal eye-piece upon the ceiling of the observing-room. Blurred and
indistinct through over-magnifying, yet with a new meaning to me,
_there_ the vast abysm lies pictur