Soap Bubbles
and the Forces which Mould Them

THE FORCES WHICH MOULD THEM. 145 good after two years’ keeping. I have given these directions very fully, not because I feel sure that all the details are essential, but because it exactly describes the way I happen to make it, and because I have never found any other solution so good. Castille soap, Price’s glycerine, and rain-water will almost certainly answer every purpose, and the same proportions will probably be found to work well. Rings for Bubbles. These may be made of any kind of wire. I have used tinned iron about one-twentieth of an inch in diameter. The joint should be smoothly soldered without lumps. If solder- ing is a difficulty, then use the thinnest wire that is stiff enough to support the bubbles steadily, and make the joint by twisting the end of the wire round two or three times. Rings two inches in diameter are convenient. I have seen that dipping the rings in melted paraffin is recommended, but I have not found any advantage from this. The nicest material for the light rings is thin aluminium wire, about as thick as a fine pin (No. 26 to 30,