7 
regulated by no laws and reducible to no fixed 
principles. Thus, Mr. Croll argues that if the 
extremes of heat and cold in winter and sum- 
mer be greater, a colder climate will prevail, 
for there will be more snow and ice accumu- 
lated in the cold winter than the hot summer 
can melt, a result produced by the vapour 
(aided by the shelter from the sun’s rays) susr 
pended in consequence of the aqueous evapora- 
tion ; hence we should get glacial periods, 
when the orbit of the earth is at its greatest 
eccentricity at those parts of the earth’s 
surface where it is winter when the earth is in 
aphelion ; carboniferous or hot periods, where 
it is winter in perihelion j and normal or tem- 
perate periods, when the excentrieity of orbit 
is at a minimum; all these would gradually 
slide into each other, and produce at long dis- 
tant periods alternations of cold and heat, 
several of which we actually observe in geo- 
logical records. Mr. Caroll’s computation 
would make it certainly not less than 
100,000 years since the last glacial epoch, pro- 
bably it is much more. In the old theories the 
apparent changes on the earth’s surface were 
accounted for by convulsions and cataclysms ; 
the referring past changes to causes similar to 
those now in operation remained uninvestigated 
until the present century. It is much more 
easy to invent a special cause than to trace out 
the influencj of slow continuous change ; the 
love of the marvellous is so much more attrac- 
tive than the patient investigation of truth, that 
we find it to have prevailed almost universally 
in the early stages of science. In geology a 
deluge or a volcano was supplied. In paloeon- 
tology a new race was created whenever theory 
required it ; how such new races began, the 
theorist did not stop inquire. A curious specu- 
lator might address to a palaeontologist of even 
recent date, words of Lucretius which Mr. 
Grove paraphrases thus : “ You have aban- 
doned the belief in one primaeval creation at 
one point of time ; you cannot assert that an 
elephant existed when the first Saurians roamed 
over earth and water: Without, then, in 
any way limiting Almighty power, if an 
elephant were created without progenitors, the 
first elephant must, in some way or other, 
have physically arrived on this earth. Whence 
did he come ? Did he fall from the sky (i i.e . 
from the interplanetary space) ? Did he 
rise moulded out of a mass of amorphous 
earth or rock ? Did he appear out of the cleft 
of a tree P If he had no antecedent progeni- 
tors, some such beginning must be assigned to 
him.” Mr. Grove knows of no scientific writer 
who has, since the discoveries of geology have 
become familiar, ventured to present in intel- 
ligible terms any definite notion of how such 
an event could have occurred. Those who do 
not adopt some view of continuity are content 
to say, God willed it ; but would it not be 
more reverent and more philosophical to in- 
quire by observation and experiment, and to 
reason from induction and analogy, as to the 
probabilities of such frequent miraculous inter- 
ventions ? The President knows that he 
touches on delicate ground, and that a long 
time may elapse before that calm inquiry after 
truth which it is the object of scientific institu- 
tions to promote can be fully maintained ; but 
he trusted that the members of the British 
Association are sufficiently free from prejudice, 
whatever their opinions may be, to admit an 
inquiry into the general question whether 
what we term species are and have been 
rigidly limited, and have at numerous periods 
been created complete and unchangeable, or 
whether, in some mode or other, they have not 
gradually and indefinitely varied, and whether 
the changes due to the influence of surround- 
ing circumstances, to efforts to accommodate 
themselves to surrounding changes, to what is 
called natural selection, or to the necessity of 
yielding to superior force in the struggle for 
existence, as maintained by our illustrious 
couutryman Darwin, have not so modified 
organisms as to enable them to exist under 
changed conditions. Mr. Grove puts forward 
no theory of his own, nor does he argue in sup- 
port of any special theory, but having endea- 
voured to show how, as science advances, the 
continuity of natural phenomena becomes 
more apparent, he thinks it would be cowardice 
not to present some of the main arguments for 
and against continuity as applied to the history 
of organic beings. The question whether 
among the smallest and apparently the most 
elementary forms of organic life, spontaneous 
generation obtains, has recently formed the 
subject of experiment and discussion in Prance. 
Although we see no such phenomenon as the 
formation of an animal such as an elephant, or 
a tree such as an oak, excepting from a parent 
which resembles it, yet, if the microscope re- 
vealed to us organisms, smaller but equally 
complex, so formed without having been 
reproduced, it would render it not im- 
probable that such might have been the 
case with larger organic beings. The general 
opinion is, that when such precautions are 
taken as exclude from the substance submitted 
to experiment all possibility of germs from 
the atmosphere being introduced, as by passing 
the air which is to support the life of the ani- 
malcules through tubes heated to redness and 
other precautions, no formation of organisms 
takes place. The question may not be finally 
determined, but the balance of experiment and 
opinion is against spontaneous generation. In 
proportion as our means of scrutiny become 
more searching, heterogeny, or the develop- 
ment of organisms without generation from 
parents of similar organism, has been gradually 
driven from higher to lower forms of life, so 
that if some apparent exceptions still exist, 
they are of the lowest and simplest forms ; 
and these exceptions may probably be removed, 
if not removed already, by a more searching 
