Report of the Kew Committee. 



83 



Mr. Marth is still engaged on the reduction to heliocentric elements 

 of the pictures for 1864 to 1868 inclusive. 



All of these operations have been conducted under the direction and 

 at the expense of Mr. De La Rue. 



The eye-observations of the sun, after the method of Hofrath 

 Schwabe, have been made daily, when possible, as described in the 

 Report for 1872, in order for the present to maintain the continuity 

 of the Kew record of sun-spots. 



Extra Observations. — The Solar-radiation Thermometers are still 

 observed daily, and a new form of the instrument designed by Pro- 

 fessor G. C. Foster, is at present undergoing trial. 



The question of observing Solar Radiation having been referred by 

 the Meteorological Council to the Kew Committee, a sub-committee 

 has been appointed to take the whole subject into consideration. 



The Campbell Sundial described in the 1875 Report, continues in 

 action, and the improved form of the instrument, giving a separate 

 record for every day, of the duration of sunshine, has been regu- 

 larly worked throughout the year and its curves tabulated. 



A paper comparing the relative amount of sunshine recorded by this 

 instrument during the year 1877, with the amount registered at the 

 Royal Observatory, Greenwich, by a similar apparatus, has been read 

 by the Superintendent before the Meteorological Society, and pub- 

 lished in their Quarterly Report, vol. iv, No. 28. It shows that the 

 difference in the total duration of sunshine observed at the two 

 stations, which amounted to 171 hours in the year, was in great mea- 

 sure due to the preponderance of westerly winds, which carry the 

 smoke of the metropolis over the Royal Observatory. 



A copy of the Kew instrument, constructed by Mr. Browning for 

 the Brussels Observatory, has been compared at the Observatory ; and 

 another instrument, with a new form of mounting, designed by Mr. 

 R. J. Lecky, F.R.A.S., is at present being tried. 



Wind Component Integrator. — This instrument, at the time of the 

 last Report, was working temporarily, attached to the Kew Anemo- 

 graph. This arrangement was found, however, to interfere with the 

 regular action of the latter instrument, and accordingly its own cups 

 and vane, sent over by Professor von Oettingen, have been fitted to it 

 by Mr. R. W. Munro ; and with the exception of a small period, during 

 which it was under repair (one of the cups having been carried away 

 by a high wind), it has been in good action. A comparison of its 

 indications with those of the ordinary instrument will shortly be 

 made. 



Plioto-neplwscope. — This instrument, designed by Professor Stokes 

 and Mr. F. Galton for the purpose of photographing clouds at the 

 time of their passage across the zenith, has been the subject of experi- 

 ment for some time, with a view of its adoption as a means of trigo- 



G 2 



