478 



Report of the Keio Committee. 



Violle'sActinometer. — The Committee have undertaken at the request 

 of the Meteorological Council to make observations with a pair of 

 Violle's actinometers. These consist of two delicate mercurial ther- 

 mometers encased, the one in a well-blackened hollow metal sphere, 

 the other in the centre of a similar sphere thickly gilded and 

 having a highly polished surface. They have been suitably mounted, 

 and are taken out on sunny days, placed side by side in the open air, 

 and then alternately exposed to the Solar rays, and shielded from its 

 action, the behaviour of the thermometers being noted. Up to the 

 present date, 230 observations have been made with them on seven days. 



Solar Physics. — The Committee have handed over to the Solar 

 Physics Committee, with the view of their utilisation, the collection 

 of Solar Negatives from 1858 to 1872 taken at Cranford and at Kew, 

 as well as a large number of undistributed copies of the papers on 

 Solar Physics by Messrs. de la Rue, Stewart, and Loewy. 



IV. Experimental Work. 



Photo-nephograph. — As it was found that a much more suitable 

 site was offered by the roof of the new building for the working of 

 the cloud cameras, the pedestal was removed from the position it 

 formerly occupied and set up on gratings placed on the new roof, the 

 necessary alterations being effected in the electrical attachments. 

 Opportunity was taken at the same time of replacing, by new wire, 

 about 30 yards of the cable which had become damaged during the 

 building operations. As, however, the question of the most coti- 

 venient way of utilising the cloud pictures is still under consideration 

 by the Meteorological Council, no photographs have been taken during 

 the past year. 



Pendulum Observations. — In November last, the series of pendulum 

 observations at the Observatory, as arranged by General Walker, 

 were successfully carried out, and the apparatus then dismounted and 

 conveyed to the Royal Observatory, Greenwich, where it was set up 

 in the Record Room. Mr. Hollis was instructed by Mr. Constable, 

 the Kew Observer, in the routine of observing in the manner employed 

 at Kew, but the operations had to be postponed for several months 

 owing to a pressure of other work at the Greenwich Observatory. 

 The pendulum swings were commenced in June and are now com- 

 pleted, and the results, at both Kew and Greenwich, are being 

 prepared for publication. 



Anemometer Constants. — With a view of examining into the accuracy 

 of the graduation of the small anemometers or air-meters that are very 

 much employed in measuring draughts and air-currents in mine- 

 shafts, galleries, and similar places, a whirling apparatus was roughly 

 constructed with materials at hand and set up in the Optical Room. 



