2 Improvements in Physical Science [Jan. 
Il. ASTRONOMY. 
Three astronomical papers have been published in the Philoso- 
phical Transactions for 1815. 
1. A memoir by Dr. Herschel on the Satellites of the Georgian 
Planet. It contains an immense collection of observations, con- 
tinued from 1787 to 1810. The existence of two satellites has been 
established completely ; the first of which performs a synodical re- 
volution about the planet in 8? 16" 56’ 5:2”; the second, in 13¢ 
11" 8’ 59”. He has rendered it probable that there exists a satel- 
lite nearer the planet than either of these two, and that there are 
likewise several exterior satellites. But the extreme remoteness of 
this planet renders the determination of these points exceedingly 
difficult. 
2. A Memoir on the Dispersive Power of the Atmosphere, and 
its Effect on Astronomical Observations, by Mr. Stephen Lee. The 
author observes that stars of different colours must be differently 
refracted, and that the apparent altitude of the sun must vary 
according to the colour of the dark glass through which he is viewed. 
That the fixed stars differ from each other in respect to the compo- 
sition of their light is evident to the naked eye ; but this difference 
becomes still more perceptible when they are viewed through a 
_ prism properly adapted to the eye-piece of a reflecting telescope. 
The planets also differ much from each other in this respect. These 
considerations inducing Mr. Lee to suspect that the dispersive power 
of the atmosphere must be sufficient in many eases to produce con- 
siderable effect on astronomical observations, he made a set of 
observations on the diameter of the planet Mars while in opposition 
in 1813. From a great number of observations, he found that the 
deviation of the extreme rays of light was between ,1; and 1, part 
of the total refraction. Mr. Lee conceives that the disagreement 
between the latitude of a place deduced from observations of cir- 
cumpolar stars, and from observations of the sun, may be traced to 
the use of dark glasses. ‘io a similar cause he ascribes some other 
discordances in astronomical observations. 
3. Determination of the North Polar Distances, and proper Mo- 
tions of 30 fixed Stars, by the Astronomer Royal. The table of the 
north polar distances of these stars laid before the Royal Society in 
1813 was so accurate, that Mr. Pond found no occasion, from his 
subsequent observations, to make a greater alteration in any of them 
than -1, of asecond. By comparing his own catalogue with that of 
Dr. Bradley in 1756, he has ascertained the proper motions of these 
stars during a period of 58 years. The annual proper motion of the 
Pole Star is — 0°057” ; that of 6 Urs Minoris, + 0-1”. 
Ill. ACOUSTICS. 
Some objections to Dalton’s theory of gases have been started in 
Germany. The most important of these is, that if the gases are not 
elastic to each other, every sound ought to be repeated four times, 
