The Sun.
London, England, 1869-04-09 00:00:00

THE APPROACIIIXO 711 A N-611'S OF VENUS

The Daily A-ems discusses the approaching transits of
Venus, and calls attention to the means which have been
taken to observe them. The Royal Geographical Society
has been discussing wine important questions with regard
to the subject. Commander Davis, in describing the pre-
parations which were to be made for Antarctic expeditions
to observe the transit of 1882, quoted the statement made
by the Astronomer Royal, that the transit of 1874 will be
wholly unsuited to the particular mode of observation he
was considering. This statement has now been called in
question. M. Puiseux, a well-known French mathematician,
and Mr. Proctor, the author of a treatise on the planet
Saturn, have, by independent processes, arrived at the con-
clusion that astronomers cannot do better than to apply
to the transit of 1874 the old-fashioned and simpler
mode of observation which Mr. Airy had rejected as un-
suitable. As usually applied, the method of determining
the same distance by observing Venus in transit resolves
itself into a comparison of the durations of transit, as seen
from a northern and from a southern station. The greater
the difference of dui ation the more effective is the method.
If one could find one station where the transit bsgan as
early as possible, and ended, as late as possible, and
another where these conditions were reversed, we should
have precisely what is wanted. But astronomers
have to be content with only an approach to
these conditions, and it happens that in 1874 the
approach will not be so close as could he wished.
The Astronomer Royal, therefore, suggested that instead
of sending out observers to places where the whole transit
could be seen, we should send one set of observers to a
place where the transit will begin as early as possible,
another set to a place where it will begin as late as pos-
sible ; and two other sets to places where the transit will
end as early and as late as possible. As the four positions
thus marked out are separated by thousands of milesfrom
each other, it would be requisite that the exact longitudes
of each place of observation should be ascertained,
and very accurate chronometers made use of, in
order that it might be possible afterwards to
effectually compare the observations inter se. An
error of a single second in determining the true
local time of any place would vitiate the resulting esti-
mate of the sun's distance in an appreciable manner. M.
Puiseux has shewn that the simpler method can be made
use of effectively. He names places where the differ-
ence of the duration of transit is as much as 30 minutes,
whereas the greatest interval by the Astronomer's Royal's
method is but 22 minutes. But Mr. Proctor goes much
further than this. He shews that by attending only
to the particular appearances which observers are
required to watch, the superiority of the simpler
method is much more strikingly exhibited; and not only
so, but that the transit of 1874 is shewn to be clearly
superior to the transit of 1882, and also to the famous
transit of 1769. The appearances referred to are what
are called the internal contacts of the planet with
the sun. All calculations of the sun's distance have been
founded on observations of the moments when the planet
is just fully seen within the disc of the sun, after
ingress, and before egress. Neither Mr. Airy
nor M. Puiseux seems to have paid sufficient
attention to this circumstance. It now appears
that whereas the greatest observed difference of dura-
tion was less than 24 minutes in 3769 and will
be bat 28 minutes at the outside in 1882, it will be possible
to find places in 1874 giving a difference of fully 36 minutes.
The full mathematical details of the correction are pre-
seated in the monthly notices of the Astronomical Society,
and the next number of the Quarterly Journal of Science
will contain a more popular statement of the facts which
are in question. Fortunately there is still time to make
preparations for applying the simpler mode of observation
suggested, should astronomers decide that M.
bstatementsme are
thevery
valid. Antarctic e
discussed journey journeys
Commander llr hr t o
Davis six weeks ago.
stations

FAITII AND RELIGIOUS FEELING.—Faith is by no
means identical with the religious faculty and feeling. If
it were4then the Scotch would he the mostreligious people
that eve existed, because their whole being is inwoven
with certain dogmas, especially the dogma of predestina-
tion. tittle emotion, however, enters into their religion,
little imagination, and no sentiment or presentiment of
the mySterious in its most awful aspects. They are
God-fearing rather than devout. A Scotch sermon
is a longiargument, often a very able argument, seldom a
passiorialte appeal. I am not aware that, though they
have mitten controversial and theological works in
abundrince, the Scotch have ever produced a single pro.
perly devotional book. They go on singing, Sunday after
Sunda ,;the Psalms of David in metre, and fiercely resist
the i*.Ciinction of hymns an
from
and of
the sweetest
4evotiont food.—" Scottish Ohara I InstrumentalandlubTlic
tiding themselvesiti,
th" Lig i f,. SW Otos a-sivc,
ti
ciir_ 414 amino, ,