A liquid issuing from a tube is pulled downwards by the force of gravitation, and therefore is always tending to fall. At first, when the drop is small, the action of gravity is overcome by the surface tension of the liquid; but as the drop grows in size and increases in weight, a point arrives at which the surface tension is overpowered. Then commences the formation of a neck, which grows narrower under the stretching force exerted by the weight of the drop, until rupture takes place. Now if we wish to make the process more gradual, it will be necessary to reduce the effect of gravity, as we cannot increase the surface tension. We have already seen how this may be done in connexion with liquid spheres—indeed, we were able to cancel the influence of gravity entirely, by surrounding the working liquid by a second liquid of exactly equal density. We require now, however, to allow the downward pull of the drop ultimately to overcome the surface tension, and we must therefore form the drop in a less dense liquid. If this surrounding liquid be only slightly less dense, we should be able to produce a very large drop; and if we make its growth slow we may observe the whole process of formation and separation with the unaided eye. [Illustration: __Fig._ 13.—Apparatus for forming ascending or descending drops of liquids._] Now it so happens that we have to hand two liquids which, without any preparation, fulfil our requirements. Orthotoluidine, at temperatures below 75° F. or 24° C., is denser than water of equal temperature. At 75° F. their densities are identical; and as the ordinary temperature of a room lies between 60° and 70° F., water, under the prevailing conditions, will be slightly the less dense of the two, and will therefore form a suitable medium in which to form a large drop of orthotoluidine. I therefore run this red-coloured liquid into water from a funnel controlled by a tap (Fig. 13), and in order to make a large drop the end of the stem is widened to a diameter of 1½ inches. It is best, when starting, to place the end of the stem in contact with the surface of the water, as the first quantity of orthotoluidine which runs down then spreads over the surface and attaches itself to the rim of the widened end of the stem. The tap is regulated so that the liquid flows out slowly, and we may now watch the formation of the drop. At first it is nearly hemispherical in shape; gradually, as you see, it becomes more elongated; now the part near the top commences to narrow, forming a neck, which, under the growing weight of the lower portion, is stretched until it breaks, setting the large drop free (Figs. 14 to 18). And then follows the droplet; very small by comparison with the big drop, but plainly visible (Figs. 19 and 20). The graceful outline of the drop at all stages of the formation must appeal to all who possess an eye for beauty in form; free-flowing curves that no artist could surpass,