Notes 245 



pose the mullions may have been taken out without injuring 

 the general effect of the building ; while, in some rooms, the 

 ancient form of window with large mullions may be preserved. 

 Those who have noticed the cheerfulness and magnificence 

 of plate-glass in the large Gothic windows of Cashiobury and 

 Cobham will not regret the want of modern sashes in an an- 

 cient palace. 



47 THEORY OF COLOURS AND SHADOWS 



By the Rev. Dr. Milner, F.R.S. 

 DEAN OF CARLISLE, AND PRESIDENT OF QUEEn's COLLEGE, CAMBRIDGE 



1. Several years ago some curious questions concerning the 

 colours of the shadows of bodies were proposed to me by an 

 ingenious and philosophical friend, who himself can paint very 

 well, and is an excellent judge of colours. He first mentioned 

 the following facts : 



2. Supposing a piece of writing-paper to be weakly illumined 

 by white light, and, at the same time, to have a strong red light 

 thrown upon it by any contrivance, the shadow upon the paper, 

 of a body placed in the said red light, will be green. 



3. Or, vice versa^ if a strong green light be thrown upon the 

 same paper, the shadow of a body placed in the green light will 

 be red. 



4. Under similar circumstances, the shadow of a body inter- 

 cepting orange-coloured light will be blue, purple, or almost 

 violet, according as the orange light contains more or less red; 

 and vice versa. 



5. And lastly, the shadow of a body which intercepts yellow 

 light will be purple, and vice versa. 



6. The phenomena just mentioned may be exhibited in sev- 

 eral ways. The weak white light may always be had in a dark 

 room, either by admitting a small portion of daylight or by 

 means of a small lamp or wax taper, the light of which is 

 sufficiently white for the purpose; and in regard to the strong 

 coloured lights, they are also easily procured, either by using 



