proceedings: philosophical society 153 



tive absorption; he also questioned the extent to which the sun may 

 be treated as a black body, particularly in the ultra-violet region. 

 Mr. Humphreys asked whether there was any connection found be- 

 tween the daily fluctuations of the solar constant and the changing 

 barometric pressure at the same time. Mr. Abbot stated that the 

 work did not indicate selective absorption since the differences from all 

 wave-lengths are not found to be in the same sense; there appears to 

 be no connection between the daily variations of solar constant and 

 barometric pressure. 



Mr. L. A. Bauer then presented a paper entitled, Corresponding 

 changes in the earth's magnetic field and the solar radiation. Recent in- 

 vestigations with the aid of later solar and magnetic data have con- 

 firmed the author's preliminary conclusions of 1914 and 1915. It 

 is again found in the majority of cases (about 80 per cent) that in- 

 creased intensity of solar radiation, as shown by the changes in solar- 

 constant values possessing the accuracy of those of the Smithsonian 

 Institution, is accompanied by an appreciable decrease in the constant 

 used as a measure of the intensity of the earth's magnetic field. While 

 the magnetic effect, observed on the average, is such as accompanies 

 the heating of a magnet, it is, apparently, not to be referred to such a 

 cause. A preliminary examination of the magnetic effects in different 

 parts of the earth indicates that the seat of the system of forces caus- 

 ing the effects is not within the earth itself but in the regions above us. 

 In conclusion, it was pointed out that, from the standpoint of terres- 

 trial magnetism, observations dependent solely upon the thermal en- 

 ergy of solar radiation can not be given any greater significance than 

 that they may indicate some change in solar activity. Thus changes 

 in the solar constant may not be regarded as a true, or adequate, 

 measure of the various ionizing agencies (ultra-violet light, corpuscu- 

 lar radiations, electrons impinging upon our atmosphere, etc.) which 

 are, at present, believed to be ultimately the cause of the magnetic 

 effects. To the pyrheliometer, the bolometer, and meteorological ap- 

 pliances, must be added the magnetic needle, if we wish to get as com- 

 plete a representation as possible of the various effects attributable to 

 our sun, directly or indirectly. 



Discussion: Mr. Swann stated that computations, assuming the 

 total energy of the spectrum could be wholly absorbed in the upper 

 atmosphere, indicated the resulting ionization would be only 1/100 of 

 that required to account for the diurnal variation if we accept Schuster's 

 theory. Mere heat and light radiation could not account for the 

 conductivity. 



INFORMAL COMMUNICATIONS 



An apparatus for making hydrostatic weighings, developed for finding 

 the volumes of precision weights, was shown and described by Mr. 

 A. T. Pienkowsky. The chief aim in designing the apparatus was 

 to allow fairly accurate measurements to be repeated quickly, and to 

 provide for the easy handling of several different sized objects in succes- 

 sion. A scale-pan, essentially a flat grid, is suspended by a wire coated 



