On a new Method of viewing the Chromosphere . 105 



January 9, 1873. 



WILLIAM SHARPEY, M.D., Vice-President, in the Chair. 



The following communications were read : — 



I. " On a new Method of viewing the Chromosphere." By J. 

 N. Lockyer, F.R.S., and G. M. Seabroke. Received No 

 vember 6, 1872. 



The observations made by slitless spectroscopes during the eclipse of 

 Dec. 11, 1871, led one of us early this year to the conclusion that the 

 most convenient and labour-saving contrivance for the daily observation 

 of the chromosphere would be to photograph daily the image of a ring- 

 slit, which should be coincident with an image of the chromosphere itself. 



The same idea has since occurred to the other. 



We therefore beg leave to send in a joint communication to the Royal 

 Society on the subject, showing the manner in which this kind of observa- 

 tion can be carried out, remarking that, although the method still requires 

 some instrumental details, which will make its working more perfect, 

 images of the chromosphere, almost in its entirety, have already been seen on 

 several days during the present month and the latter part of last month. 



The adaptation of this method to a telespectroscope will be seen at a 

 glance from the accompanying drawing. 



O 



Diaphragm showing annulus, the breadth of which may be v tried to suit the state of 



the air. 



The annulus is viewed and brought to focus by looking through apertures in the side 



of the tubes. 



A. Sliding eye-tube of telescope. B. Tube screwing into eye- tube. C. Tube sliding 

 inside B, and carrying lens D and diaphragm E. F. Lenses bringing image of 

 diaphragm to a focus at the place generally occupied by the slit of the spectroscope 

 G-. Collimator of spectroscope. 



The image of the sun is brought to focus on a diaphragm having a circular 

 disk of brass (in the centre) of the same size as the sun's image, so that the 

 sun's light is obstructed and the chromospheric light is allowed to pass. 



YOL. IXT. K 



