Soap-Bubble. A soap-bubble, as it floats in the light of the sun, reflects to the eye an endless variety of the most gorgeous tints of colours. Newton showed, that to each of these tints corresponds a certain thickness of the substance forming the bubble : in fact, he showed, in general, that all transparent substances, when reduced to a certain degree of tenuity, would reflect these colours. Near the highest point of the bubble, just before it bursts, is always observed a spot which reflects no colours and appears black. Newton showed that the thicknesses of the bubble at this black point was the 2,500,000th part of an inch! Now, as the bubble at this point possesses the properties of water as essentially as does the Atlantic Ocean, it follows that the ultimate molecules forming water must have less dimensions than this thickness.