222 Royal Society .-—Messrs, Lockyer and Seabroke 



which gives X for points situated on the axis for which as is not less 

 than(6+c-f/). 



January 9, 1873. — "William Sharpey, M.D., Vice-President, in 

 the Chair. 



The following communication was read : — 



" On a new Method of viewing the Chromosphere." By J. 1ST. 

 Lockyer, F.K.S., and Gr. M. Seabroke. 



The observations made by slitless spectroscopes during the 

 eclipse of Dec. 11, 1871, led one of us early this year to the con- 

 clusion 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 

 Boyal Society on the subject, showing the manner in which this kind 

 of observation can be carried out, remarking that, although the me- 

 thod 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. 



Diaphragm showing annulus, the breadth of which may be varied 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. ¥. Lenses bringing 

 image of diapbragm to a focus at the place generally occupied by the slit of 

 the spectroscope. G. Collimator of spectroscope. 



