them a good squeeze, and draw the upper piece slightly round at the same time, and here they are as one, and all the bending and twisting I can give them will not separate them again: I have joined the lead together, not with solder, but simply by means of the attraction of the particles.
This, however, is not the best way of bringing those particles together—we have many better plans than that; and I will shew you one that will do very well for juvenile experiments. There is some alum crystallised very beautifully by nature (for all things are far more beautiful in their natural than their artificial form), and here I have some of the same alum broken into fine powder. In it I have destroyed that force of which I have placed the name on this board—Cohesion, or the attraction exerted between the particles of bodies to hold them together. Now I am going to shew you that if we take this powdered alum and some hot water, and mix them together, I shall dissolve the alum—all the particles will be separated by the water far more completely than they are here in the powder; but then, being in the water, they will
