64. These astonishing revelations of natural mysteries, fresh tidings of which crowd in upon us every day, may be likely to overwhelm all sober hesitation as to the capacities of the human mind, and to bring back that confidence which Bacon, in so much less favourable circumstances, has ventured to feel. There seem, however, to be good reasons for keeping within bounds this expectation of future improvement, which, as it has sometimes been announced in unqualified phrases, is hardly more philosophical than the vulgar supposition that the capacities of mankind are almost stationary. The phænomena of nature indeed, in all their possible combinations, are so infinite, in a popular sense of the word, that during no period, to which the human species can be conceived to reach, would they be entirely collected and registered. The case is still stronger as to the secret agencies and processes by means of which their phænomena are displayed. These have as yet, in no one instance, so far as I know, been fully ascertained. “Microscopes,” says Herschel, “have been constructed which magnify more than one thousand times in linear dimension, so that the smallest visible grain of sand may be enlarged to the appearance of one million times more bulky; yet the only impression we receive by viewing it through such a magnifier is that it reminds us of some vast fragment of a rock; while the intimate structure on which depends its colour, its hardness, and its chemical properties, remains still concealed; we do not seem to have made even an approach to a closer analysis of it by any such scrutiny.”[208] [208] Discourse on Nat. Philos., p. 191. |Limits to our knowledge by sense.|