Page:Proceedings of the Royal Society of London Vol 2.djvu/39

Rh through the fissures of this rock that the water is supposed to issue, till overpowered by the increasing column of tide, which, by its greater specific gravity, will occasion it to find vent at a level which will be more above the point at which the two fluids meet in proportion to the difference of their densities.

In confirmation of this hypothesis it is further observed, that after very stormy weather, when there is an unusual swell upon that coast, the water is discharged with an evident undulation.

Dr. Storer, however, observes, that the relative altitude to which the spring is elevated after much rain, rather militates against its correctness; and he would expect the additional force of the column of spring water at such times to produce an opposite effect, by enabling it to overcome the same column of sea-water during a longer period in each tide.

As it seemed probable that the subject may be elucidated by an acquaintance with the peculiarities of the springs in the neighbourhood, the author remarks, that upon the Wolds behind Bridlington there is very little water during summer and autumn; but in the course of two or three weeks after the commencement of frost, the springs begin to run copiously, and in some instances even with considerable impetuosity. 



The author having, in former experiments on the depolarization of light by a mixture of resin and bees' wax, had reason to suppose that the effects were modified by pressure, now examines the effects of pressure on a class of substances which, from their elasticity, will restore themselves after removal of the force applied, and thence admit of greater variety in the repetition of the experiments. By employing animal jellies, he had an opportunity of giving them any degree of tenacity that might be wished.

A small cylinder of jelly being placed upright between two plates of glass, had at first no power of depolarization. By gradual drying at its circumference, it soon began to depolarize at that part; and as it became thereby more dense than at its centre, it had the power of a concave lens. At the end of three weeks it seemed dried to the centre, and had then lost both these properties; but by forcible pressure, which it could now bear without injury, it depolarized completely during the continuance of the pressure; but upon its removal, says Dr. Brewster, it resumed its uncrystallized state.

The author next employed isinglass jelly, brought nearly to the consistence of caoutchouc, which, after standing one day, had acquired the depolarizing power even when cut into thin slices; and