178 
the upper surface of which is black in the L. timedus, and 
white, tinged with greyish towards the base, in the Irish 
species. On looking to their osteology, some slight differ- 
ences are observable in the head; the comparatively more 
horizontal direction of the lumbar vertebra in the Irish hare 
is conspicuous, and likewise the relative shortness of its tail, 
which, as first recorded by Mr. Eyton, contains three 
vertebra less than that of the English species, 13 only being 
possessed by the former, and 16 by the latter animal. 
The occasional whiteness of fur in the Irish hare is 
believed by the author to be a consequence of age, and not 
regulated by the law that is understood to affect the Alpine 
hare, which is considered to change its dark summer fur to 
white at the commencement of every winter. 
The economy and habits of the Irish hare, which generally 
correspond with those of the common species, are, together 
with a comparative description of form, colour, &c., very 
fully detailed in this paper. 
Mr. Robert Mallet read a paper ‘‘on an hitherto un- 
observed Force of Elevation and Degradation.” 
The author maintains, that the forces producing geologic 
changes are either mechanical or chemical, and that the 
reaction of these forces, when co-existent, as is usually the 
case, often gives rise to a third order of forces, which may 
be denominated molecular forces, or those which, without 
altering the atomic composition of bodies, affect the arrange- 
ment and aggregation of their particles—modify their specific 
gravity—their action on light, heat, electricity, &c., and 
produce the varied differences of ductility, hardness, brittle- 
ness, &c. &c. While chemical and mechanical forces have 
been applied to geology, those of this latter class have been 
almost wholly overlooked. 
Of the several known molecular forces, those producing 
change of volume and of specific gravity are perhaps the 
