Report of the Kew Committee. 105 



in Kew Gardens were resumed in November 1874, after an interval of a 

 few months, and were continued until March, when the experiments 

 were concluded, having lasted over nearly two years. The results have 

 been sent to the Meteorological Office, at the expense of which Depart- 

 ment the investigation was conducted. 



A commencement has been made of the observation of Solar Badiation 

 at Kew ; and Thermometers for that purpose (" Black bulbs in vacuo" 

 by different makers) have been placed in the grounds and read regularly. 



The Eegistering Sundial invented by Mr. J. E. Campbell, E.G.S., 

 which has been in operation for several years at the Office of the Local 

 Government Board, 8 Bichmond Terrace, Whitehall, has been trans- 

 ferred to Kew, and is in action at the Observatory. It consists of a 

 glass sphere and wooden bowl, and the effect is measured by the amount 

 of wood charred by the sun's action in the course of six months. Ex- 

 periments are in progress to obtain a satisfactory daily record of the 

 duration of the sun's heating-action by a similar method. 



Verifications. — This department of the Observatory continues to ex- 

 hibit increased activity, and, in more than one respect, important steps 

 have been taken with the view of augmenting its efficiency. 



The following magnetic instruments were verified : — 



2 Unifilars for the Arctic Expedition. 



2 Declinometers for the Arctic Expedition. 



2 Barrow's Dip-circles for the Arctic Expedition. 



3 Box's Circles for the Arctic Expedition. 



1 Box's Circle for Staff- Commander Creak. 

 1 Dip-needle for H.M.S. « Challenger.' 



Constants were determined for 3 Magnets for the Admiralty. 



The set of Magnetographs ordered by Capt. C. Bujazon for the Marine 

 Observatory of San Bernando, near Cadiz, have been constructed, and, 

 after verification at Kew, have been forwarded. 



A similar set of Magnetographs has been ordered by Dr. Vogel for 

 the new Astrophysical Observatory at Botsdam, near Berlin. 



A TJnifilar and Dip-circle have been obtained for Badre B. Denza, of 

 the Observatory of Moncalieri, and have been forwarded to him after 

 verification. 



The following meteorological instruments have been verified, this 

 portion of the work being entrusted to Mr. T. W. Baker, assisted by 

 Messrs. Foster, Constable, and "Welsh : — 



Barometers, Standards 67 



„ Marine and Station 126 



193 

 Aneroids 21 



