Using these data--with Stefan's law of decrease of radiation as the 4th power of the temperature--a mathematical friend finds that the temperature of the moon's surface would be reduced during the lunar night to nearly 200 deg.

F.absolute (equal to-258 deg.

F.).
_More Rapid Loss of Heat by the Moon._ Although such a calculation as the above may afford us a good approximation to the rate of loss of heat by Mars with its very scanty atmosphere, we have now good evidence that in the case of the moon the loss is much more rapid.

Two independent workers have investigated this subject with very accordant results--Dr.Boeddicker, with Lord Rosse's 3-foot reflector and a Thermopile to measure the heat, and Mr.Frank Very, with a glass reflector of 12 inches diameter and the Bolometer invented by Mr.Langley.The very striking and unexpected fact in which these observers agree is the sudden disappearance of much of the stored-up heat during the comparatively short duration of a total eclipse of the moon--less than two hours of complete darkness, and about twice that period of partial obscuration.
Dr.Boeddicker was unable to detect any appreciable heat at the period of greatest obscuration; but, owing to the extreme sensitiveness of the Bolometer, Mr.Very ascertained that those parts of the surface which had been longest in the shadow still emitted heat "to the amount of one per cent.

of the heat to be expected from the full moon." This however is the amount of radiation measured by the Bolometer, and to get the temperature of the radiating surface we must apply Stefan's law of the 4th power.