432 



Sun Viewing and Drawing. 



Hence it is of great importance that these large hand 

 drawings should be diligently maintained by as many competent 

 observers and draughtsmen as possible, until Heliophotography 

 shall have happily succeeded in obtaining abundance of detail 

 of solar phenomena, on a very much larger scale, and with far 

 more distinctness than has yet been accomplished, save in a, 

 few isolated instances. The difficulties, indeed, which beset 

 Heliophotography are immense ; but who can say what may 

 not at last be accomplished by the talent, perseverance, and 

 liberality of De La Rue, Selwyn, and their coadjutors and 

 assistants, in the comparatively new and wonderful art of 

 celestial photography ? Very much has been done already, 

 and we sanguinely hope that more is yet to follow. 



But we must now proceed to describe how these drawings 



were accomplished. 

 And first, as re- 

 gards the best 

 method of project- 

 ing the solar image. 

 Select a cham- 

 ber having a win- 

 dow, if possible, 

 looking towards 

 the east as well 

 as south ; and hav- 

 ing effectually 

 closed up all other 

 windows or sources 

 of light, fasten 

 neatly in the one 

 remaining window 

 a portable sort of 

 wooden frame, 

 covered with Ame- 

 rican cloth (A in 

 Fig.), or some other 

 substance imper- 

 vious to light. In 

 the centre of this 

 cloth cut out a ver- 

 tical aperture about 

 an inch or so broader 

 than the tube of 

 your telescope, and 

 about two feet in 

 length. In front 

 slender wooden bars, 



A 



J A E 



A 



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i i 



-j 



Mr P "- ; f 



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\v 



[ U c 



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p 



) 



F 





1- 



A 



A 



DARKENING SHUTTEE, FOR VIEWING THE SUN 

 BY PROJECTION ON A SCREEN. 



of this aperture, set up, by means of 



