160 Chronicles of Science. [ Jan. 
the aqueous vapour which exists within 10 feet of the earth’s surface 
on a day of average humidity. Wet weather, saturating the atmosphere 
with vapour, acts as a warm blanket to the earth, whilst cold frosty 
weather, by drying the air, allows more heat to radiate from the earth, 
and produces a still greater degree of cold. The relation which these 
facts bear to many obscure phenomena of climate is fully discussed by 
Professor Tyndall in the paper already mentioned. 
The destructive energy of hot water in steam-boiler explosions has 
been made the subject of an investigation by the Astronomer Royal.* As 
the result of many experiments, he concludes that the destructive energy 
of one cubic foot of water, at the temperature which produces a pressure 
of 60 lbs. to the square inch, is equal to that of 1 1b. of gunpowder. 
A very sensitive thermometer has been described by Dr. Joule.t 
It consists of a glass tube, 2 feet long and 4 inches in diameter, divided 
longitudinally by a blackened pasteboard diaphragm, with spaces of 
about an inch at the top and bottom. In the top space a bit of mag- 
netized sewing-needle, furnished with a glass index, is suspended by 
a single filament of silk. The arrangement is similar to that of a 
bratticed coal-pit shaft, and the slightest excess of temperature of one 
side over that of the other occasions a circulation of air which ascends 
on the heated side, and, after passing across the glass index, descends 
on the other side. As a proof of the extreme sensibility of the instru- 
ment, it is able to detect the heat radiated by the moon. A beam of 
moonlight was admitted through a slit in a shutter, and as the ray 
passed gradually across the instrument, the index was deflected several 
degrees, showing that the air in the instrument had been raised a few 
ten-thousandths of a degree in temperature by the moon’s rays. 
Many researches on the intensity of the electrical current developed 
by different thermo-electro pairs have been published by M. Edmond 
Becquerel ; he finds that the best thermo-electric couple is composed of 
platinum and palladium, the two metals being unaltered by heat, and 
the intensity of the current increasing regularly with the temperature. 
This electric pyrometer was compared with graduated air-thermo- 
meters, and by this means many high temperatures have been able to 
be expressed in centigrade degrees. We give a few:—The boiling 
point of sulphur is 448° ; the fusing point of silver is 916°; the fusing 
point of gold, 1,037°; the fusing point of palladium, between 1,560° 
and 1,380°; the fusing point of platinum, between 1,460° and 1,480° ; 
the highest temperature of a fragment of magnesia, before the oxy- 
hydrogen blow-pipe, 1,600° ; whilst the limit of temperature of the 
positive carbon of the voltaic are is 2,000°. 
A convenient gas-furnace for experimental purposes has long been 
wanted. Many contrivances have been made having for their object 
the production of a furnace-heat with gas, but they have invariably 
required an artificial blast of air, thus rendering it necessary for one 
person to be in attendance, and hard at work, during the whole of the 
* British Association, Newcastle Meeting. 
+ ‘Proceedings of the Literary and Philosophical Society of Manchester,’ 
