Greenwich; and
to regard all west longitude as in arrear of British time, and all east
longitude as in advance of it. And this is the method practised by modern
navigators.

It is not, however, in obedience to any preconceived system, but by pure
accident, that our settlements in Australia and New Zealand happen to be in
accordance with this rule. The last-named country is very close upon the
verge of eastern longitude, but still it is within it, and its day is
rightly in advance of our day. But the first settlers to Botany Bay, in
1788, were actually under orders to go out by Cape Horn, and were only
forced by stress of weather to adopt the opposite course by the Cape of
Good Hope. Had they kept to their prescribed route, there cannot be a doubt
that the day of the week and month in Australia would now be a day later
than it is.

The best proof of the truth of this assertion is, that a few years
afterwards a missionary expedition was sent out to Otaheite, with respect
to which a precisely similar accident occurred; they could not weather Cape
Horn, and were forced to go round, some twice the distance out of their
way, by the Cape of Good Hope; consequently they carried with them what may
be called the eastern day, and since then that is the day observed at
Otaheite, although fully two hours within the western limit of longitude.

From this cause an actual practical anomaly has recently arisen. The French
authorities in Tahiti, in accordance with the before-mentioned rule, have
arranged their day by _western longitude_; consequently, in addition to
other points of dissent, they observe the Sabbath and other festivals one
day later than the resident English missionaries.

I have extended this explanation to a greater length than I intended, but
the subject is interesting, and not generally well understood; to do it
justice, therefore, is not compatible with brevity. Much of what I have
said is doubtless already known to your readers; nevertheless I hope it may
be useful in affording to H. the information he required, and to ESTE more
fixed notions on the subject than he seems to have entertained when he
wrote the answer referred to.

A. E. B.

Leeds.

* * * * *

PHOTOGRAPHIC CORRESPONDENCE.

_Aceto-Nitrate of Silver._--I have collected together several ounces of
aceto-nitrate of silver that has been used to excite waxed paper (iodized
by MR. CROOKES' method), and should be glad