xxxiv GENERAL SUMMARY OF SCIENTIFIC AND 



tion, being merely a consequence of their heating effect. It may, 

 however, be that the instrument, in a modified form, can be used 

 as an additional means of investigating the important question of 

 the absorption of the sun's heat by the atmosphere. Among those 

 who have published investigations on the radiometer may be men- 

 tioned Poggendorff, Carriugton, Reynolds, Stoney, Dewar, and Tait, 

 all of whom maintain that the kinematic theory of heat fully ex- 

 plains its motions. 



The subject of solar radiation has been oflacially taken up by the 

 Meteorological Society of England, which undertakes to carry on 

 the work begun by the Rev. F. W. Stowe ; the society will, however, 

 adopt the comparison of the black with the bright bulb thermom- 

 eter, both in vacuo, instead of comparing the black in vacuo with 

 the maximum temperature of the air as recorded in the shade. 



In connection with this discussion a new series of observations 

 has been begun, and eleven stations have undertaken observations 

 on the new plan, from which interesting results must be expected. 

 Among these stations is the observatory at Kew, at which the regis- 

 tering sun-dial invented by Mr. Campbell is now in action, it having 

 been already in operation for several years at Whitehall. This in- 

 strument consists of a glass sphere set in a wooden bowl ; and the 

 effect of the sun is measured by the amount of wood charred by the 

 sun's action in the course of six months. 



Mr. Roscoe appeals to the meteorological observatories of the 

 world to carry on some systematic observations upon the varying 

 chemical intensity of the direct and diffused solar light. The im- 

 proved apparatus devised by him is, he states, as simple as could be 

 wished ; he has made most minute investigations into its errors, and 

 will undertake the determination of the relative corrections with 

 respect to the apparatus belonging to other observers, if so desired. 



An elaborate work on the source and quantity of work done by 

 hot-air balloons is published by Papper,who shows that the applica- 

 tion of air balloons heated by the solar rays, as motors, in place of 

 our present machines which use coal as the source of heat and work, 

 is not likely to unite economy with moderate size. 



The important hygrometric studies of Dufour have been continued 

 by him, and form the basis of a second memoir on hygrometric diffu- 

 sion through partitions of porous earthenware. The results obtained 

 in his earlier researches are fully corroborated, and minuter investi- 

 gations have led to still further elaboration of the same complex sub- 

 ject. It would appear, however, that the hygrometer composed by 

 him originally may still be relied upon, although each special instru- 

 ment must require careful investigation and comparison with the 

 standard. This hygrometer being adapted to give continuous records 

 like that employed by Bache at Philadelphia, and being far less 

 troublesome in its operation, may possibly come into general use. 



