Dilatation of Crystals on Change of Temperature. 275 
of electrification on a plate of a given shape, when its plane 
is perpendicular to the direction of the lines of force, increase 
in an increasing proportion as the dimensions of the plate 
increase. 
IY. That the distribution of electricity on a plate is sub- 
stantially reversed when its plane is respectively parallel or 
perpendicular to the direction of the lines of force. 
V. That when the direction of the lines of force, in an 
electrolytic field, is parallel to the sides and perpendicular to 
the ends of a metallic conductor, the distribution of electricity 
thereon is similar to the distribution of electricity set up on a 
similar-shaped conductor, in air or other gaseous dielectric, 
and subjected to ordinary inductive forces. 
VI. That the power of points in accumulating electricity is, 
under the conditions set out in Y., similar to the power shown 
in air when the conductor to which they are attached is sub- 
jected to ordinary inductive forces. 
In conclusion, I would point out that our knowledge of the 
power of points to accumulate electric force, and, generally, 
of the distribution of electricity on conductors subjected to 
ordinary inductive forces in air, has been obtained under 
circumstances where it may be supposed that the direction of 
the lines of force was more or less parallel to the sides and 
perpendicular to the ends of such conductors. But I venture 
to think, seeing the close analogy which evidently exists under 
certain circumstances between the distribution of electricity 
on conductors in electrolytes and in dielectrics, that the further 
exploration of electrical distribution on conductors in air sub- 
jected to inductive forces differing in direction, will show that 
the laws governing the distribution of electricity on conductors 
in the respective electric fields are similar, if not identical. 
In other words, the distribution of electricity on metallic bodies. 
in air may be found to be as dependent upon the direction of 
the lines of force as in electrolytes. 
August 1883. 
XLI. The Dilatation of Crystals on Change of Temperature. 
By L. Fletchee, M.A., of the Mineral Department, British 
Museum ; late Fellow of University College, Oxford*. 
[Second paper.] 
[Plate IH.] 
IN a previous paper bearing the above titlef, read before the 
Crystallological Society in November 1879, the following 
properties were shown to follow from the assumption that the 
* Read before the Crystallological Societv, July 3, 1883. 
t Phil. Mag. 1880, vol. ix. p. 81. 
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