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112 least but such as are extremely slight in comparison with those which take place in the group of tints formed about the violet No. 11. There is no other fact connected with this. Such at least is my opinion, after having examined it under various aspects without being able to arrive at a satisfactory explanation. I am therefore unable to say more about it for the present.

Effect of Artificial Light during the Night.

It is an admitted fact, that we cannot judge of colours without the presence of daylight. But what changes do they undergo when viewed in the evening? The following are those that I have observed in the tints of my scale when examined at that time. The two conflicting opinions of those whom I consulted on this subject I forbear to mention.

1. The greens increase in beauty and intensity.

2. The yellows and the azure are tarnished and become deeper.

3. The blues and the indigo become greenish.

4. The violets approximate to a blue.

5. The violet-reds become more violet.

6. The first eight tijits of the scale become more like each other, and approach more nearly to the metallic colours.

7. The other tints remain nearly unchanged.

Some of those changes are produced even by day if the colours of the scale are viewed through a green crystal, and others if they are viewed through yellow or azure crystals. Artificial light is without doubt differently constituted from that of the sun: it contains probably a scanty mixture of red rays with an abundance of the yellow, green, and azure. But what is the coloured diaphragm that should be interposed in the passage of the light of day, in order to reduce it to the same proportions as that of night? The problem is an interesting one, but it remains as yet without solution.

Harmony of Colours.

My scale appears to all persons to be eminently harmonious. I have already mentioned the delight which it afforded those who saw it. I have now to add that artists are astonished not to find the green in its usual place, between the yellow and the azure colours of the second order. But I take the two finest greens in the scale, Nos. 32 and 41, and call upon the most accomplished artists to assign them a more suitable place than that which they occupy. Influenced by habit they unhesitatingly place them among the yellows and the blues of the second interval, having no doubt that this is their proper place. They are however soon undeceived by the result ; the green is found unpleasing here; the harmony is destroyed, and cannot be re-established until the colours are restored to their original position. But what is this harmony? It is an effect