22 On a Method of Cooling the 
server, 1721 miles; and that entry into the earth’s shadow 
was the true cause of the disappearance, is borne out by the 
fact that the direction of motion was fowards the axis of the 
earth’s shadow. And, on account of the extremely small dis- 
tance of the body, its change of place during flight would sufh- 
ciently account for its gradually appearing in the lower part of 
the sky when coming out of conjunction, increasing in bril- 
liancy during its flight (reaching, at its maximum, the bright- 
ness of Venus), and then slowly vanishing as it entered first 
the penumbra and then the umbra of the earth’s shadow in a 
slanting direction ; and lastly, the body can hardly fail of 
being a satellite, as its distance is so much less than that of 
a shooting-star, which M. Petit of Toulouse has pretty well 
identified as revolving about the earth in 3" 20", or at about 
3000 miles from the surface.—(Proceedings of the Royal 
Society of Edinburgh, 1849.) 
2. Method of Cooling the Atmosphere of Rooms in a Tropical 
Climate. 
After stating the case distinctly, and dwelling emphatically 
on its importance, as shewn by individual instances in pri- 
vate life, and by the statistics of the world at large, the 
author proceeded to describe the various methods adopted 
at present in India, and shewed their incapacity to meet the 
end proposed, as they merely agitated the air already in a 
room, or perniciously overloaded it with moisture. 
To take the most difficult case that could occur, he chose 
that of a country where the mean temperature of day and 
night, and summer and winter, is never below 80°, and where 
there could, consequently, be no coolness in springs or rivers, 
or in the night air; where also the atmosphere being satu- 
rated with moisture, no cold could be produced by evapora- 
tion ; and under such circumstances proposed that a method 
should be found of lowering the temperature of the air in a 
room ; doing, in fact, there, the reverse of what is effected in 
a cold room by lighting a fire. 
The principle of the plan which he brought forward was 
dependent on the property of air to increase in temperature 
on compression, and to diminish on expansion ; the air was 
