104 Report of the Kew Committee. 



tory by the Meteorological Office for the services of one of the staff to 

 take temporary charge of the Valencia Observatory, owing to the serious 

 illness of the Superintendent of that Station, the Rev. Thomas Kerr, who 

 has since died. Mr. Cullum at once consented to undertake the duty, 

 and he has remained at Valencia up to the present time. This change 

 has necessarily weakened the working power of Kew in the special de- 

 partment now under consideration ; and in consequence a certain amount 

 of arrears have accumulated, but these will be ere long cleared off. 



The only change as regards the photographic instruments has been the 

 substitution of copper chimneys for the gas-jets for the glass chimneys 

 formerly in use, an alteration which has proved to be beneficial. 



The result of a careful comparison of the thermogram tabulations at 

 the several observatories, obtained by the use of the fiducial lines traced 

 on the curves by photography, with the standard readings, has shown 

 that the original glass scales supplied (the values for which had been 

 determined at Kew in 1868) were not in all instances sufficiently exact, 

 and new scales have accordingly been supplied where requisite. 



Electrometer. — The Self-recording Electrometer continues in operation. 

 Some imperfection, of which the cause was not clearly ascertained, inter- 

 rupted the continuity of the action of the instrument in August ; but this 

 was overcome and the record resumed. Experiments for obtaining the 

 scale-value have been made by the use of a battery of 100 Bunsen's cells. 



Mr. Ellis, Superintendent of the Meteorological and Magnetic De- 

 partment at the Royal Observatory, Greenwich, has visited Kew, by 

 direction of the Astronomer Royal, in order to examine the instru- 

 ment, in the view of the possible procuring of a similar apparatus for 

 Greenwich. 



Photoheliograph. — The instrument which, in February 1873, was trans- 

 ferred to Greenwich for the use of the Astronomer Royal has been 

 reported by him to be ready for immediate return to Kew. 



The re- examination of the measurements of the Kew sun-pictures, as 

 noticed in the last Report, has been steadily carried on throughout the 

 year (at the expense of Mr. De La Rue, D.C.L.) by Mr. Whipple, assisted 

 by Mr. M'Laughlin, who has been temporarily engaged for this purpose. 



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

 Schwabe, have been made daily by Mr. Foster, when possible, as de- 

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

 the continuity of the Kew record of sun-spots. 



Extra Observations. — The experiments with a Photometer for measur- 

 ing the total intensity of daylight, w T hich has been designed by Prof. H. 

 E. Roscoe, Ph.D., have been continued during the year, as mentioned 

 in last Report. The original instrument provided by Prof. Roscoe 

 having proved defective, it was replaced by another, which remains on 

 trial. 



The observations with Thermometers at different levels on the Pagoda 



