But even when the bubbles escape into air, tiny quantities of liquid are detached; so that steam from boiling water, for example, is never entirely free from liquid. All users of steam are well acquainted with this fact. ¹ Mono-brom-benzene is better than chloroform for this experiment, but is more costly. It may be coloured with indigo. Chloroform may be coloured with iodine. *Condensation of Drops from Vapour,—Mists, Fogs and Raindrops.*—The atmosphere is the great laboratory for the manufacture of drops. It is continually receiving water in the form of vapour from the surface of the sea, from lakes, from running water, and even from snow and ice. All this vapour is ultimately turned into drops, and returned again to the surface, and to this never-ceasing exchange all the phenomena connected with the precipitation of moisture are due. The atmosphere is only capable of holding a certain quantity of water in the form of vapour, and the lower the temperature the less the capacity for invisible moisture. When fully charged, the atmosphere is said to be “saturated”—a condition realized on the small scale by air in a corked bottle containing some water, which evaporates until the air can hold no more. The maximum weight of vapour that can be held by 1 cubic metre of air at different temperatures is shown in the table:— ────────────────────────────────────────────────────────────────── Temperature. Weight of water vapour (grammes) required to Deg. C. Deg. F. saturate 1 cubic metre. ────────────────────────────────────────────────────────────────── 0 32 4·8 5 41 6·8 10 50 9·3 15 59 12·7 20 68 17·1 25 77 22·8 30 86 30·0 35 95 39·2 40 104 50·6 ──────────────────────────────────────────────────────────────────