a proof that the
astronomer's prophecy is about to be fulfilled, is not a matter of any
special importance, even in a popular sense, much less in a scientific
sense. As a rule, the total phase does not become imminent, so to speak,
until a whole hour and more has elapsed since the first contact; and
that hour will be employed by the scientific observer, less in looking
at the Sun than in looking at his instruments and apparatus. He will do
this for the purpose of making quite sure that everything will be ready
for the full utilisation to the utmost extent of the precious seconds of
time into which all his delicate observations have to be squeezed during
the total phase.

With these preliminary observations I shall proceed now to break up the
remainder of what I have to say respecting total eclipses into what
suggest themselves as convenient sectional heads.

THE MOON'S SHADOW AND THE DARKNESS IT CAUSES.

In awaiting the darkness which is expected to manifest itself an
unthinking and inexperienced observer is apt to look out for the coming
obscurity, as he looks out for night-fall half an hour or more after
sunset and during the evening twilight. The darkness of an eclipse is
all this and something more. It is something more in two senses; for the
interval of time between the commencement of an eclipse and totality is
different in duration and different in quality, so to speak, from the
diminution of daylight on the Earth which ensues as the twilight of
evening runs its course. Speaking roughly, sunset may be described as an
almost instantaneous loss of full sunlight; and the gradual loss of
daylight is noticeable even at such short intervals as from one five
minutes to another. This is by no means the case previous to a total
eclipse of the Sun. When that is about to occur, the reduction of the
effective sunlight is far more gradual. For instance, half an hour after
an eclipse has commenced more than half the Sun's disc will still be
imparting light to the Earth: but half an hour after sunset the
deficiency of daylight will be very much more marked and, if no
artificial light is at hand, very much more inconvenient.

If there should be within easy reach of the observer's post a bushy
tree, such for instance as an elm, 30 ft. or 40 ft. high, and spreading
out sufficiently for him to place himself under it in a straight line
with the Sun, and with a nice smooth surface of ground for the sun's
rays to fa