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 pro- 

 portion 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 neighbour- 

 hood, 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 con- 

 siderable impetuosity. 



On the Effects of simple Pressure in producing that Species of Cry- 

 stallization which forms two oppositely polarized Images, and exhibits 

 the complementary Colours by polarized Light. By David Brewster, 

 LL.D. F.R.S. Edin. and F.S.A. Edin. In a Letter addressed to 

 the Right Hon. Sir Joseph Banks, Bart. K.B. P.R.S. Read Ja- 

 nuary 19, 1815. [Phil. Trans. 1815, p. 60.] 



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 ad- 

 mit of greater variety in the repetition of the experiments. By em- 

 ploying animal jellies, he had an opportunity of giving them any de- 

 gree 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 pres- 

 sure, which it could now bear without injury, it depolarized com- 

 pletely 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 ac- 

 quired the depolarizing power even when cut into thin slices ; and 



