[ 53 ] 

 IX. Proceedings of Learned Societies, 



ROYAL SOCIETY. 



[Continued from vol. xxxix. p. 462.] 



March 10, 1870.— Warren De La Ru-, Esq., Vice-President, in the 



Chair. 



HPHE following communication was read : — 



" Researches on Solar Physics. — No. II. The Positions and 

 Areas of the Spots observed at Kew during the years 1864-66, also 

 the Spotted Area of the Sun's visible disk from the commencement 

 of 1832 up to May 1868." By Warren De La Rue, Esq., Ph.D., 

 F.R.S., F.R.A.S., Balfour Stewart, Esq., LL.D., F.R.S., F.R.A.S., 

 &c, and Benjamin Loewy, Esq., F.R.A.S. 



The paper commences with a continuation for the years 1864-66 

 of Tables II. and III. of a previous paper by the same authors ; it 

 then proceeds to a discussion of the value of the pictures of the 

 sun made by Hofrath Schwabe, which had been placed at the dis- 

 posal of the authors ; and the result is that these pictures, when 

 compared with simultaneous pictures taken by Carrington and by the 

 Kew heliograph, are found to be of great trustworthiness. From 

 1832 to 1854 the pictures discussed are those of Schwabe, who was the 

 only observer between these dates ; then follows the series taken by 

 Carrington, and lastly the Kew series, which began in 1862. 



A list is given of the values of the sun's spotted area for every fort- 

 night, from the beginning of 1832 up to May 1868, and also a list 

 of three-monthly values of the same, each three-monthly value being 

 the mean of the three fortnightly values which precede and of the 

 three which follow it. These three-monthly values are also given for 

 every fortnight. 



A plate is appended to the paper, in which a curve is laid down 

 representing the progress of solar disturbance as derived from the 

 three-monthly values ; and another curve is derived from this by a 

 simple process of equalization, representing the progress of the ten- 

 yearly period. The values of the latter curve, corresponding to every 

 fortnight, arc also tabulated. From this Table are derived the follow- 

 ing epochs of maxima and minima of the longer period : — 



Minimum Nov. 28, 1833. 



Maximum Dec. 21, 1836. 



Minimum Sept. 21, 1843. 



Maximum Nov. 14, 1847. 



Minimum April 21, 1856. 



Maximum Sept. 7, 1859. 



Minimum Feb. 14, 1867. 

 This exhibits a variability in the length of the whole period. 



Thus we have between 1st and 2nd minimum 9-81 years. 



2nd and 3rd do. 12 58 „ 



3rd and 4th do. 10*81 „ 



Mean of all the periods 1 1 '07 years. 



