REPORT OF THE KEW COMMITTEE. XXXV 



ture and moisture of his apartments have been forwarded by the Royal Society 

 to the Kew Observatory. 



The Indian pendulum observations are in active progress. Both Colonel 

 "Walker and Captain Basevi are in correspondence with the Observatory in 

 discussing questions relating to this work. 



The Superintendent has received JlOO from the Government Grant Com- 

 mittee of the Eoyal Society for preliminary observation with Captain Kater's 

 pendulum. These preliminary observations are in progress under the charge 

 of ilr. Loewy as observer, and have the following points in view ; — 



(1) To see by the general agreement or non-agreement of the observations 

 with each other whether Captain Kater's pendulum is still in a state to justify 

 its adoption as an instrument to give a correct determination of the length of 

 the seconds' pendulum. 



(2) To determine the true temperature correction of the pendulum, 



(3) To use Kater's pendulum, and also the Eoyal Society's invariable 

 pendulum ISTo. 8, for the purpose of determining a curve of correction for 

 atmospheric pressure, from inch to inch, at low pressures. 



The Superintendent has received £50 from the Government Grant Fund 

 of the Royal Society, to pursue the experiments on a rotating disk. 



The Kew Heliograph, in charge of Mr. De la Rue, continues to be worked 

 in a very satisfactory manner. During the past year 282 negatives have 

 been taken on 158 days, and the usual number of positives have been 

 printed from them. 



Since the last Meeting of the Association, the first set of the results ob- 

 tained by this instrument have been published at the expense of Mr. De la 

 Rue, under the following title : — " Researches on Solar Physics, by Warren 

 De la Rue, B. Stewart, and B, Loewy ; first series ; On the Nature of Sun- 

 spots." 



The present progress of the work of reduction wiU best be seen from the 

 following letter, written by Mr. De la Rue, in answer to a request made 

 through the Astronomer Royal by Padre Secchi, to know what was doing in 

 this country in the subject of Heliography. 



" 110 BunhiU Eow, August 8th, 1866. 



" Mt dear Sir, — In reference to the extract from Padre Secchi's letter, 

 I beg to supply the following information. 



" The pictures taken by means of the Kew Heliograph are all measured by 

 means of my Micrometer ; the positions of the spots are then reduced to dis- 

 tances in terms (fractional parts) of the sun's radius, and the angles of position 

 corrected for any error in the position of the wires. 



" Pictures of the Pagoda are taken from time to time, and the measure- 

 ments of the various galleries of the Pagoda serve to determine the optical 

 distortion of the Sun's image, and the corrections to be applied to the Sun- 

 pictures. 



" The heliocentric latitudes and longitudes of the spots are then calculated. 



" The areas of the spots and the penumbra are also measured, and the areas 

 corrected for perspective are tabulated in terms (fractional parts) of the area 

 of the sun's disk. 



" The areas of the spots (fee. on aU of Carrington's original pictures have re- 

 cently been measured, and an account of these measurements will be shortly 

 published. 



" Padre Secchi wiU be able to judge, from the foregoing statement, whetiier 

 it will be worth while to undertake the work he proposes. 



c2 



