Curiosities of Science. 37 



are hit during battle according to the colour of their dress in 

 the following order : red is the most fatal colour ; the least 

 fatal, Austrian gray. The proportions are, red, 12 ; rifle-green, 

 7 ; brown, 6 ; Austrian bluish-gray, 5. Jameson's Journal, 1853. 



TRANSMUTATION OF TOPAZ. 



Yellow topazes may be converted into pink by heat ; but it 

 is a mistake to suppose that in the process the yellow colour is 

 changed into pink : the fact is, that one of the pencils being 

 yellow and the other pink, the yellow is discharged by heat, 

 thus leaving the pink unimpaired. 



COLOURS AND TINTS. 



M. Chevreul, the Directeur des Gobelins, has presented to the 

 French Academy a plan for a universal chromatic scale, and a 

 methodical classification of all imaginable colours. Mayer, a 

 professor at Gottingen, calculated that the different combina- 

 tions of primitive colours produced 819 different tints; but M. 

 Chevreul established not less than 14,424, all very distinct and 

 easily recognised, all of course proceeding from the three pri- 

 mitive simple colours of the solar spectrum, red, yellow, and 

 blue. For example, he states that in the violet there are twenty- 

 eight colours, and in the dahlia forty-two. 



OBJECTS REALLY OF NO COLOUR. 



A body appears to be of the colour which it reflects ; as we 

 see it only by reflected rays, it can but appear of the colour 

 of those rays. Thus grass is green because it absorbs all except 

 the green rays. Flowers, in the same manner, reflect the va- 

 rious colours of which they appear to us : the rose, the red rays ; 

 the violet, the blue; the daffodil, the yellow, &c. But these 

 are not the permanent colours of the grass and flowers; for 

 wherever you see these colours, the objects must be illuminated; 

 and light, from whatever source it proceeds, is of the same na- 

 ture, composed of the various coloured rays which paint the 

 grass, the flowers, and every coloured object in nature. Objects 

 in the dark have no colour, or are black, which is the same 

 thing. You can never see objects without light. Light is com- 

 posed of colours, therefore there can be no light without co- 

 lours ; and though every object is black or without colour in 

 the dark, it becomes coloured as soon as it becomes visible. 



THE DIORAMA WHY SO PERFECT AN ILLUSION. 



Because when an object is viewed at so great a distance 

 that the optic axes of both eyes are sensibly parallel when 

 directed towards it, the perspective projections of it, seen by 



