16-4 ON COLOUR. PaetI. 



depth of tone, the loss of light is proportionally great, and 

 such a blue shade takes away one quarter of the light. 

 Light, therefore, should be sought which has as little as pos- 

 sible of the red or yellow rays ; and the whiter gas, requiring 

 a blue shade of lighter tone, gives a greater quantity of light, 

 without the necessity of increasing its strength in order to 

 overcome the effect of a deeper blue glass. 



With regard to other coloured inks on various papers, the 

 only one of much value is blue ; owing to their being defi- 

 cient in contrast ; except when red is employed together with 

 black ink, to distinguish words on white paper. 



These are a summary of the observations respecting the 

 use of coloured papers, which I have been enabled to collect 

 through the kindness of Mr. Babbage, and by means of the 

 interesting and extensive investigations he has made ; and we 

 may hope that they will be given to the public in their full 

 extent, with all the necessary illustrations, by their talented 

 author. 



XXII. I have been careful to point out more than once 

 certain errors to be avoided in judging of colours, and to show 

 what is necessary for the study of their harmonious combina- 

 tions ; and as these cannot be too frequently insisted upon, I 

 shall repeat some of the most important of them under the 

 following heads : — 



1. The eye is the proper judge of colour, and the percep- 

 tion of colour is a natural gift. (pp. 55, 64.) 



2. We should abstain from theories till the subject is 

 understood, (pp. 3, 6, 7, 58, 92.) 



3. Flowers, and other ornaments, should be conventional, 

 not direct copies of natural objects ; nor should you tread on 

 these in carpets, nor walk on the tracery of architecture, 

 (pp. 18, 46, and see Part II. §§27, 32.) 



4. The three primary colours, blue, red, and yellow, which 

 are a concord, should predominate in ornamentation ; yet 

 scarlet (which is really a compound colour) generally looks 



