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Show 312 SMALL VALUE OF TESTIMONY Upon difficult subjects it is astonishing t? what an extent the multiplication of these little differences will in the end mislead us, if vve do not keep the whole chain carefully in view; for in twenty successive occurrences we may attend carefully to eac?, and compare it with the one immediately before 1t, and find the very same apparent similari~.y in each of those comparisons; and yet the dlfference.s, unseen in the individual cases, may so mount up m the aggregate as that the last m.ay be . unlike the first-or even the very reverse of 1t. With careless observers who are satisfied with a few of the external and' more obvious circumstances, that is much more frequently the case;. and as they who publish their opinions or concluswns to the world are not always the most close and accurate observers, !hat is the reason why so many errors have crept mto the science and the systems of natural history ; and as many of these errors are fortified .by high authority, and all of them by some authonty (for there always are people ?o fo~wa~d in their b~lief that the very fact of being m pnnt IS an authonty to them), they are very difficult to be reduced. The only means of doing that is by going bt1ck to the beginning of the series, that is, to nature itself; and hence the superiority of kno"':ledge which we get from our own aetna~ ~bservat10~1 to knowledge of any other kind: But It ~s only a little way that that will carry us without assistance. W. e must see the whole succession; and the cases m which we have that opportunity are few, while those for which a whole lifetime is too short are very many. It is in those cases of which we can P.ersonally observe only a part that the co-operatwn of society is of much value. We have the record of the past for that part of the succession which happened before we were .born, and we ~ave the intelligence of the present time for that which takt>s place when we are not preseut; and thus, though IN NATURAL JUSTORY. Sl3 we cannot, in these cases, have so certain know· ledge as we have of that which fal1s under our own immed·· te observation, we have it as well established as it <!an be by testimony. Cases such as that of the entire destruction of a whole tribe, ?r. species, of organic beings, do not come ev.en w1t~m the scope of testimony; for history, bemg chiefly confined to the transactions of men, and, genera1ly speakin![, even to a very limited number of them, is silent with regard to the others even in those instances which from the circumstan~ tial evidence we would be led to co11clude had fallen within the period over which it extends. In the instance above quoted, there is every circumstantial proof that the castle was built while the neighbouring ground was wood and copse., and not peat-bog: and the appearance of a castle with hewn revetments ·and grouted walls bespeaks a degree of civilization higher than that of any people a1torrether without a history. But still there is not a single trace remaining; and that is ?.t once a proof that those peovle neglected the observation of nature, and of the loss which we now sustain from its being so neglected -and .that, not at one rcm?te point merely, but at all p_?mts.. We h~ve, for mstance, the hi~tory of the mhabitants of London, the more remarkable buildings, and even the very ~treets, hnt where is the history o.f the Thames a1 d its va1ley 1 and yet . both may, n:jeed mu:st, h:we underaone many changes since the ~oman legions first ;ppeared on the banks of the nver. So also every river and river's valley must ~1ave chanrred; and those changes must have had an mftuence on the weather, the climate, the season~, the plants, the animals, and the whole natural history of the country. in so far as that can ~e affected .by the changes of time, or those of any thmg- that time changes. But for the want of observatiOn and record, the whole of that is lost. We are consequently ignorant of the great natural Dd |