There are twenty other experiments I might shew you to illustrate this power of cohesion of the particles of liquids. For instance, what would you propose to me if, having lost the stopper out of this alcohol bottle, I should want to close it speedily with something near at hand. Well, a bit of paper would not do, but a piece of linen cloth would, or some of this cotton wool which I have here. I will put a tuft of it into the neck of the alcohol bottle, and you see, when I turn it upside down, that it is perfectly well stoppered, so far as the alcohol is concerned; the air can pass through, but the alcohol cannot. And if I were to take an oil vessel, this plan would do equally well, for in former times they used to send us oil from Italy in flasks stoppered only with cotton wool (at the present time the cotton is put in after the oil has arrived here, but formerly it used to be sent so stoppered). Now, if it were not for the particles of liquid cohering together, this alcohol would run out; and if I had time, I could have shewn you a vessel with the top, bottom, and sides altogether formed like a sieve, and yet it would hold water, owing to this cohesion. You have now seen that the solid water can become fluid by the addition of heat, owing to this lessening the attractive force between its particles, and yet you see that there is a good deal of attractive force remaining behind. I want now to take you another step beyond. We saw that if we continued applying heat to the water (as indeed happened with our piece of ice here), that we did at last break up that attraction which holds the liquid together; and I am about to take some ether (any other liquid would do, but ether makes a better experiment for my purpose), in order to illustrate what will happen when this cohesion is broken up. Now, this liquid ether, if exposed to a very low temperature, will become a solid; but if we apply heat to it, it becomes vapour, and I want to shew you the enormous bulk of the substance in this new form--when we make ice into water, we lessen its bulk, but when we convert water into steam, we increase it to an enormous extent. You see it is very clear that as I apply heat to the liquid I diminish its attraction of cohesion--it is now boiling, and I will set fire to the vapour, so that you may be enabled to judge of the space occupied by the ether in this form by the size of its flame, and you now see what an enormously bulky flame I get from that small volume of ether below. The heat from the spirit-lamp is now being consumed, not in making the ether any warmer, but in converting it into vapour; and if I desired to catch this vapour and condense it (as I could without much difficulty), I should have to do the same as if I wished to convert steam into water and water into ice: in either case it would be necessary to increase the attraction of the particles, by cold or otherwise. So largely is the bulk occupied by the particles increased