418 Royal Society. 
series of luminous sectors ; the inner and outer series being negative, 
and the intermediate series positive. The polarizing structure of 
the cornea is negative, and it depolarizes very high tints at its junc- 
tion with the sclerotic coat. When a slice cut from the sclerotica 
nearly perpendicularly to the surfaces, and with parallel faces, is 
exposed to polarized light, it exhibits the system of biaxal rectilineal 
fringes, exactly like those in a plate of glass heated by boiling wa- 
ter or oil, when in the act of rapid cooling. The same alternation 
of properties with regard to polarization in the successive strata of 
the substance of the crystalline lenses is exhibited by other fishes 
which the author examined. 
With respect to the final cause of these highly complicated ar- 
rangements, it is reasonable to conceive that the gradually increas- 
ing density of the fibres in each successive stratum from the surface 
to the centre is intended to correct spherical aberration : but the 
design of the other properties resulting from the arrangement of the 
fibres with reference to septa, in all their variations of number and 
position, and more especially the alternations of positive and nega- 
tive structures, as exhibited by the action of the different strata in 
polarized light, has not even excited the ingenuity of conjecture, 
and will probably remain among the numerous problems destined to 
exercise the sagacity of another age. 
Jan. 28.—A paper was read, entitled, “ Discussion of Tide Ob- 
servations made at Liverpool.” By J. W. Lubbock, Esq., F.R.S. 
The chief purpose which the author has in view in presenting the 
tables accompanying this paper, which are a continuation of those 
published in the Philosophical Transactions for 1835, and are 
founded on the observations instituted by Mr. Hutchinson at Liver- 
pool, is to exhibit the diurnal inequality in the height of high water, 
which is.scarcely sensible in the river Thames, but which at Liver- 
pool amounts to more than a foot. The diurnal inequality in the 
interval appears to be insensible. 
The author has further ascertained that Bernoulli’s formule ex- 
pressing the height of the tide, deduced from his theory of the tides, 
present a very remarkable accordance with observation. 
Feb.4.-—“‘ Geometrical Investigations concerning the Phenomena 
of Terrestrial Magnetism: Second Series,-—On the number of points 
at which a magnetic needle can take a position vertical to the Karth’s 
surface.” By Thomas Stephens Davies, Esq., F.R.S. Lond. and 
Edin., F.R.A.S., of the Royal Military Academy, Woolwich. 
This paper is intended as a continuation of the one by the same 
author published in the last volume of the Philosophical Transac- 
tions* ; in which it was proposed to investigate the mathematical 
consequences of the hypothesis of the earth being a magnet with 
two poles, or centres of force, situated anywhere either within, or 
at the surface, and of equal intensity, but of contrary characters : 
with the ultimate view of verifying this hypothesis by comparing its 
results, so deduced, with the phenomena furnished by observation. 
* An abstract of Mr. Davies’s former paper appeared in Lond. and Edinb, 
Phil. Mag., vol. vi. p. 302-305.—Epir. 
