524 Meeting of the British Association. [ Oct., 
for our descendants in the tenth generation to warm their dwellings 
or propel their locomotives. 
The two very remarkable applications of the convertibility of 
force, attained by the experiments of Mr. Wilde and Mr. Holz, 
promised results of extended application, and were aptly described 
as showing how, by a mere formal disposition of matter, one force 
could be converted into another; and that not to the limited extent 
hitherto attained, but to an extent co-ordinate, or nearly so, with 
the increased actual force, so that, by a mere change in the arrange-~ 
ment of apparatus, a means of absorbing and again eliminating in a 
new form a given force might be obtained to an indefinite extent. 
As we may, in a not very distant future, need, for the daily uses of 
mankind, heat, light, and mechanical force, and find our present 
resources exhausted, the more we can invent new modes of conyer- 
sion of forces, the more prospect we have of practically supplymg 
such want. 
Rapidly glancing at the considerable strides which were being 
made in physiology, by studying the relation of organized bodies 
to external forces, the speaker passed on to the facts recently brought 
to light by geological inquiries, which, while on the one hand they 
afforded striking evidence of continuity, on the other, by the breaks 
in the record, might be used as arguments against it ; and supposing 
that the geological formation was of a continuous character, there 
came the question whether the different characters of the fossils 
represented absolute permanent varieties, or might be explained by 
gradual modifying changes. 
The subject to which the President devoted most attention was 
the always popular one of the origin of species, and the question 
whether, what we term species, are and haye been rigidly limited, 
and have at numerous periods been created complete and unchange- 
able; or whether, in some mode or other, they have not gradually 
and indefinitely varied; and whether the changes due to the in- 
fluence of surrounding circumstances, to efforts to accommodate 
themselves to surrounding changes, to what is called natural 
selection, or to the necessity of yielding to superior force im the 
struggle for existence, as maintained by our illustrious countryman, 
Darwin, have not so modified organisms as to enable them to exist 
under changed conditions. ‘The difficulty of producing intermediate 
offspring from what are termed distinct species, and the infecundity 
in many instances of hybrids, have been used as strong arguments 
against continuity of succession ; on the other hand, it might be said 
that long-continued variation through countless generations had given 
rise to such differences of physical character, that reproduction was 
difficult in some cases, and in others impossible. In favour of this 
latter view the following illustration was adduced: Suppose M to 
represent a parent race, whose offspring, by successive changes 
