412 



SCIENCE, 



[Vol. VI., No. 144. 



order to bring them into harmony with the facts 

 of modern society. The postulates selected are 

 those referring to the transferability of labor and 

 capital respectively. 



After a short discussion of the reasons for the 

 general neglect into which EngHsh poUtical econ- 

 omy has of late fallen, in which he gives nearly 

 all reasons except the right one, viz. , that it is an 

 outlived theory, the author proceeds to show 

 that the Ricardian assumption of the easy and 

 rapid transferability of labor and capital among 

 various industries never has been true, and is not 

 true now, though it may be true in the distant 

 future. A more complete vindication of the 

 justice of the attacks on Ricardo's system, so 

 far as it is claimed to be a satisfactory expla- 

 nation of our modern industrial economy, could 

 scarcely be desired. Had Mr. Bagehot lived to 

 finish the great work of which these essays were 

 to form a part, it can scarcely be doubted that he 

 would have followed out his premises to their 

 legitimate conclusions, and finally have been 

 found where he belonged, — among the opponents, 

 instead of among the restaters, of 'orthodoxy.' 



C. R. 



TEMPERATURE OF THE MOON'S SUR- 

 FACE. 



Professor Langley's two most important dis- 

 coveries — 1°, that the greater part of the energy in 

 the solar spectrum is way below the visible red ; 

 and, 2°, that our atmosphere is more and more 

 transparent to radiant energy the greater its wave- 

 length — promise to bear fruit in many directions. 

 In his paper on the temperature of the surface of 

 the moon,' one of their ajDplications is shown in the 

 complete upsetting of the long-cherished idea that 

 the temperature of the moon's surface rises to 200° 

 or 300° F. during the lunar day, and falls about 

 as far below zero in the lunar night. First enun- 

 ciated as a theory by Sir John Herschel, the 

 only experimental evidence upon which it has 

 rested has been the observations of lunar radia- 

 tion by the present Earl of Rosse, to wliich Pro- 

 fessor Langley takes no exception, so far as the 

 experimental results are concerned, but from 

 their interpretation by Lord Rosse, he enth-ely dis- 

 sents. This interpretation rests upon the assump- 

 tions, 1°, that solar radiation is principally con- 

 fined to luminous vibrations ; 2°, that about 92 per 

 cent of these are transmitted by glass ; and, 3°, that 

 only 1.6 per cent of the obscure rays are trans- 

 mitted by glass. The first has already been shown 



1 Memoirs of the NatioNal academy of sciences, vol. iii. 

 pt. i , 2d memoir. On the temperature of the surface of 

 the moon. By S. P. Langley. Washington, Government, 



1885. 4°. 



to be entirely wrong, and, when it is remembered 

 that Professor Langley found over two-thirds of 

 the total energy in the solar spectrum, from a 

 glass prism, to lie below the visible red, nothing 

 further need be said as to the non-conclusiveness of 

 any deductions from the above assumptions. 



Professor Langley's observations on Mt. Whitney 

 lead him to the conclusion that, were it not for 

 our atmosphere, the surface of the earth, even 

 under continuous direct sunshine, would be at a 

 temperature of only about 48° C. above that of 

 surrounding space (whatever that may be), at any 

 rate low enough to freeze every thing up solid, 

 perhaps even the gases ; and he concludes that the 

 moon is in this condition unless it has an appre- 

 ciably absorbing atmosphere, of which there are 

 only some uncertain suggestions at present. 



Attacking the problem entirely anew, he speaks 

 of its importance as follows : — 



'" The amount of heat received from the moon, 

 and the dependent question as to the temperature 

 of the lunar surface, are subjects of greater inter- 

 est to us than might at first appear. They are 

 even ones in which we may be said to have a 

 material concern, for, until we know the tempera- 

 ture which an airless planet would attain in the 

 sun's rays, we can have no accurate knowledge of 

 the extent to which the atmosphere of our own 

 planet contributes to its heat, nor of some of 

 the most important conditions of our own ex- 

 istence." 



Professor Langley describes important improve- 

 ments in the galvanometer used with his bolom- 

 eter, so that with the combination of the two he is 

 now able, when the needle is damped to a period 

 of 10s-, to make Imm. on the scale correspond to a 

 current of only 0.000,000,001,3 of an ampere, or 

 indicate a difference of temperature of only 

 0°. 000,016 C. As regards precision of measure- 

 ment, the probable error of a single observation is 

 only about 2 per cent of the total amount of lunar 

 radiation, while in Lord Rosse's work the probable 

 eiTor of the mean of a series of 10 observations 

 was 19 per cent, thus giving one of the former a 

 weight equal to several hundred of the latter, to 

 say nothing of its far greater freedom from con- 

 stant errors. 



With this apparatus, and with all the other re- 

 finements and precautions against error which 

 invariably accompany all of Professor Langley's 

 work, he has been making the following investi- 

 gations : — 



1°. Du-ect measurement of lunar heat compared 

 with solar. 2°. Comparison of moon's heat with 

 that of Leslie cube (hot water). 3°. Transmission 

 of lunar heat by the earth's atmosphere. 4°. 

 Comparative transmission of glass for lunar and 



