REPORT OF THE KEW COMMITTEE. XXXV 



have been printed from each, some of which have been given to men of 

 science interested in this branch of research. 



The negatives are being reduced under the superintendence of Mr. De 

 la Rue, and by means of an instrument of his own construction, which he 

 has generously presented to the Kew Committee. Mr. B. Loewy has been 

 engaged in the reduction, which he is executing satisfactorily. 



It was mentioned in last Report that an addition to the Micrometer was 

 in the course of construction, by means of which the proportion of the sun's 

 disk obscured by spots might be conveniently measured. This arrangement 

 is now completed; and the materials for measurement have been greatly in- 

 creased through the kindness of Mr. Carrington, who has placed his original 

 drawings, in which the size and appearance of the spots are delineated with 

 great fidelity, at the disposal of the Kew Observatory. It may be desirable 

 to state in a few words the proposed method of exhibiting the results of 

 these reductions. In the progress of this branch of knowledge observers have 

 been led to recognize certain laws which represent the average behaviour of 

 sun-spots ; but to all of these laws there are individual exceptions. In this 

 state of things it is probable that our knowledge of the subject will ulti- 

 mately be advanced, not only by a study of those groups which behave in a 

 normal manner, but also by a study of those which are exceptions in their 

 behaviour to the general rule; and on this account it has been thought desi- 

 rable to publish the results in such a way that anyone may be able to study 

 the appearance and behaviour — in fact the whole history — of any one group. 



In order to accomplish this, a lens is being made by Dallmeyer, by means 

 of which individual groups may be magnified to a scale on which the diameter 

 of the sun will be equal in size to two feet. 



The sun-spots continue to be observed after the method of Hofrath Schwabe, 

 of Dessau. 



As Kew is the first public institution which has taken up the subject of 

 sun-spots, and as it is intended to continue the method of numbering groups 

 so long and successfully adopted by Hofrath Schwabe, it was thought desirable 

 to endeavour to procure, if possible, for this countr}- the original drawings made 

 by this eminent and assiduous observer during a course of about forty years; 

 A joint letter by Mr. De la Rue and Mr. Stewart was consequently addressed 

 to Hofrath Schwabe ; and the following answer to it was soon received. 



" Gentlemen, — The request contained in your letter, although in the highest 

 degree honourable and complimentary to me, and although it gives me an op- 

 portunity to show the Royal Astronomical Society my gratitude for the Royal 

 Medal granted to me, has still cost me some struggle before complying with it; 

 for it is not easy to part with what has given me very often much pleasure 

 and enjoyment as a compensation for the labour - devoted to the work. 



" But in complying with your desire I do so on one condition, viz. that you 

 would grant me permission to obtain the observations back again at any time 

 that I should be desirous of looking into them, during the short time of life 

 still left to me. I do not think that I shall have an occasion to avail myself 

 of the permission asked for ; but permit me kindly to believe that it is in my 

 power to do so. After my death you may consider the whole of the observa- 

 tions as the property of the Royal Astronomical Society. 



" Please to write me if you are willing to agree to the above desire, and 

 I shall then immediately send you my astronomical diaries, &c. from 1825 to the 

 end of 1864. " I remain, Gentlemen, 



" Tours very faithfully, 



" S. H. Schwabe." 

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