366 
NATURE 
to answer this purpose, even with an ordinary balloon), 
but we think the management of the balloon may be very 
well left to Prof. Wise, whose opinion on all practical 
points of aérostation is probably of more value than that 
of any other man living. Of all the persons who have 
devoted themselves professionally to ballooning as a 
source of income, Prof. Wise is certainly the ablest, and 
his work on Aéronautics shows him to be possessed of 
considerable scientific claims. The project could not, 
therefore, be in better hands ; and considering the origi- 
nality and boldness displayed by Prof. Wise in several of 
his very numerous ascents, there is every reason to believe 
that nothing will be left undone to bring it to a successful 
issue. In all the technical matters relating to the balloon, 
therefore, Prof. Wise may be well trusted to take the best 
course ; and with regard to the meteorological questions 
involved by consulting not only American meteorologists 
but also Mr. Glaisher and other gentlemen who have 
studied the question of the winds in relation to aérostation, 
it is clear that-he intends to leave no stone unturned to 
obtain the best information attainable, and, at all events, 
merit success. 
MAYNE’S SIDEREAL DIAL 
HIS instrument consists of two moveable circles, 
which may be made of brass or pasteboard, placed 
in a common watch-case, The lower and outer one shows 
the hours doubled up to XXIV., and divided into 
quarters. The upper one, which is also inner, shows the 
sixty minutes, 5, 10, &c. This circle is a narrow one, 
and works on the plain inmost rim of the lower one, so as 
to admit of the hours being seen outside the minutes. 
Each circle being set to show at the top of the case, 
where the XII. of the watch comes, the “Sidereal Time — 
at Mean Noon” (given in the Nautical Almanack for each 
day in the year), the watch is placed in the case, and will 
continue to show the sidereal time corresponding to mean 
time approximately for six hours, after which interval the 
minute circle should be Auwt ox one minute to ensure 
greater exactness. 
This will be found a near enough approximation for the 
amateur observer, using an equatorial instrument, and 
this simple method will be found to save an infinite 
amount of trouble zz finding objects whose R.A. ts re- 
corded in a catalogue, to those who, like the inventor, are 
unprovided with a sidereal clock. 
Mr. Norman Lockyer has suggested as an improve- 
ment, the use of a watch with the seconds’ hand in the 
centre ; this would necessitate a third, and still inner 
circle for the sixty seconds, by which, indeed, subject 
to an hourly correction of, say ten seconds being 
Z~ut on, the dial would be rendered accurate enough 
for rough transit observations; and this circle and 
seconds hand have been added to the original design 
in the woodcut, where the dial is set to V. (}) 47°10, the 
Sidereal Time at Mean Noon for the 18th June, 1873, the 
hands of the watch representing IV. (4) 32°12, which gives 
the corresponding Sidereal Time X. 19°22 (or applying the 
last-named correction, say 45 seconds for 43 hours), X, 
20°7. 
It is as well perhaps, though scarcely needful, to add 
(for no one would be likely to make a mistake of 12 hours) 
that as the dial in the Example also reads XVII. (?) 47"10, 
and as the mean time by the watch may be A.M. or P.M., 
the observer should bear in mind which half of the 24 
hours, both astronomical and mean, he is working in, ) 
The third or seconds circle is not indispensable, as the 
seconds hand, even in the ordinary position, can be made 
to fulfil its object, by setting it at noon to the Sidereal 
Second on the meridian ; thus, in the Example, it would 
be set to 10, instead of to Zero, when the dial is set at 
noon, the correction for the equivalent of the lapsed in- 
terval being applied subsequently as required. But this 
involves altering the watch, which is objectionable ; the 
use of the third, or szconds’ circle, is therefore recom- 
mended, for although the seconds’ hand, as placed in 
most watches, would not actually Aoznt to the Sidereal 
second, it is easy to refer the Joszdion of the mean second 
to the corresponding part of the watch’s face, where the - 
third circle can be read off at once. 
ASHTON MAYNE, Captain, 
Bombay Staff Corps, 
Care of Messrs. Henry S, King & Co., 
65, Cornhill, London, E.C. 
