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have now got a great amount of relative thought, and we may 
go on till we believe, without difficulty and without danger of 
error, that the sea at one time flowed over the rock in which 
this shell-form lies imbedded. So long as the facts are duly 
observed, and the inferential thoughts derived from their com- 
parison are manifestly related to the facts, and beyond reason- 
able doubt, so long we are gathering real science m its two 
great branches of trustworthy instruction. . 
But, as we have indicated, there is a third kind of geological 
thought, which is of a value very different from that of the 
other two. This consists of speculation, which, so far as dis- 
covery has gone, has no realities to represent. The universe 
of waking dreams, to which this introduces us, consists ot all 
the possibilities of falsehood as well as of all those of trut . 
It is the region from which, we humbly think, true science 
warns us away. That which is, and so may be known, as dis- 
tinguished from that which is not, but may be conceived, is the 
proper object of science. It is very important, when we would 
trace the relations of geological science to the Sacred Scrip- 
tures, to consider whether we mean the relations of our hrst 
two divisions of thought, or the relations of that so-called y e0 ~ 
logy, which is chiefly composed of conjecture. Because of the 
extremely speculative tendencies of scientific men, it ^ as be- 
come painfully necessary that we should sift most carefully that 
which is presented, even by the highest authorities, as geolo- 
gical science; so that we may be able to distinguish between 
truth which is the logical result of real discovery, and doctrine 
held as above all price, but which may be abandoned to-morrow 
by those who are to-day its most earnest advocates. Because 
of the fond partiality, too, with which favourite hypotheses aio 
almost worshipped, and on account of which every opposing 
idea is disliked, it is needful that we take up, and examine with 
great care, views that have been scouted by scientific leaders 
and their followers as worthless. 
Almost all truth has been thus treated for a time by t e 
rulers of public opinion during whose reign it has been dis- 
covered. To those who have not yet attended to the evidence 
from which it really springs, and who are more in love with 
speculation than with real science, every new truth will appear 
conjectural, it may be even preposterous; while conjecture, 
which has no evidence whatever to support it, may seem 
highly reasonable, only because it happens to accord with 
some preconceived notion. 
It is in connection with this part of our subject tha . *ve 
come upon the phrase “ negative .evidence” At first sight 
one would naturally imagine that this means really ‘ evidence. 
