9. OUR author after preparing water with soap, so as to render it very tenacious, blew it up into a bubble, and placing it under a glass, that it might not be irregularly agitated by the air, observed as the water by subsiding changed the thickness of the bubble, making it gradually less and less till the bubble broke; there successively appeared colours at the top of the bubble, which spread themselves into rings surrounding the top and descending more and more, till they vanished at the bottom in the same order in which they appeared[301]. The colours emerged in this order: first red, then blue; to which succeeded red a second time, and blue immediately followed; after that red a third time, succeeded by blue; to which followed a fourth red, but succeeded by green; after this a more numerous order of colours, first red, then yellow, next green, and after that blue, and at last purple; then again red, yellow, green, blue, violet followed each other in order; and in the last place red, yellow, white, blue; to which succeeded a dark spot, which reflected scarce any light, though our author found it did make some very obscure reflection, for the image of the sun or a candle might be faintly discerned upon it; and this last spot spread itself more and more, till the bubble at last broke. These colours were not simple and uncompounded colours, like those which are exhibited by the prism, when due care is taken to separate them; but were made by a various mixture of those simple colours, as will be shewn in the next chapter: whence these colours, to which I have given the name of blue, green, or red, were not all alike, but differed as follows. The blue, which appeared next the dark spot, was a pure colour, but very faint, resembling the sky-colour; the white next to it a very strong and intense white, brighter much than the white, which the bubble reflected, before any of the colours appeared. The yellow which preceded this was at first pretty good, but soon grew dilute; and the red which went before the yellow at first gave a tincture of scarlet inclining to violet, but soon changed into a brighter colour; the violet of the next series was deep with little or no redness in it; the blue a brisk colour, but came much short of the blue in the next order; the green was but dilute and pale; the yellow and red were very bright and full, the best of all the yellows which appeared among any of the colours: in the preceding orders the purple was reddish, but the blue, as was just now said, the brightest of all; the green pretty lively better than in the order which appeared before it, though that was a good willow green; the yellow but small in quantity, though bright; the red of this order not very pure: those which appeared before yet more obscure, being very dilute and dirty; as were likewise the three first blues.