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XXI. Researches on Solar Physics. — No. II. The Positions and Areas of the Spots 
observed at Kew during the years 1864, 1865, 1866, also the Spotted Area of 
the Suns visible disk from the commencement of 1832 up to May 1868. By 
Warren De La Lite, Psq., P.C.L, V.P.P.S., F.P.A.S., Balfour Stewart, Esq., 
LL.P., F.P.S., F.RA.S., Superintendent of the Kew Observatory , and Benjamin 
Loeayy, Esq., F.P.A.S. 
Received February 15, — E,oad March 10, 1870. 
20. In a paper presented to the Society and published in the Philosophical Transactions 
for 1869 (vol. clix. p. 1), we have given a full description of the method adopted by us 
for ascertaining the positions and areas of the various sun-spots observed at Kew, and 
Ave have likewise, in Tables II. and III. of that paper, given the areas and the positions 
determined after the method described by us, for the various sun-spots of the years 1862 
and 1863. In the present paper Ave give the same elements for the years 1864, 1865, 
and 1866, forming Tables II. and III., so that these Tables in our present paper form 
a continuation of the Tables bearing the same number in our previous paper. 
We have stated elsewhere that Hofratii Sciiavabe, of Dessau, had very generously 
put into our hands the valuable collection of drawings of the solar disk made by him 
during the course of about forty years, and thus it became an object of importance to 
us to fix upon some method of testing the value of these drawings, and of extracting 
from them what information they might contain. 
Method of examination of Schwabe’s drawings. 
21. A cursory inspection of these drawings revealed the existence of several progressive 
stages in accuracy of delineation, from the time of their commencement in 1825 to that 
of their termination in 1867. By the commencement of the year 1832 the indefatigable 
observer had evidently matured his system to such an extent as to give (no doubt, with 
considerable precision) the shape and area of each group, although it was not until the 
commencement of 1840 that he had finally fixed upon that exceedingly good system of 
delineation which he thenceforth pursued up to the time when he discontinued his 
observations. 
Between the latter part of 1832 and the beginning of 1840 the circle representing the 
solar disk had in these drawings a diameter equal to 2-08 inches nearly, Avhile after 1840 
this was very slightly increased, being sometimes as great as 2*15 inches. There Avas 
thus no material alteration in the scale from the latter part of 1832 up to the end of 
mdccclxx. 3 H 
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