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knowledge, but it is essential to our progress to remember the clear distinction between them, and ia keep the mind open and attentive to fresh evidence, because it may at any time bring ns nearer to the absolute truth.

We know that we exist; that we feel pleasure and pain; that two and two make four; that the whole is greater than its parts; that there are such things as light and darkness, warmth and cold; that the rainbow is curved and coloured; that our cat has four legs, and our brother only two. These are all direct perceptions of truth, whether derived from the senses or from reason. But we only believe that we shall exist at any future time; that certain acts always produces pleasure and others always pain; that we could go to a grocer and buy a pound of sugar for five-pence; that the earth is spherical and revolves round the sun; that every cat has four legs, or every man only two. These are inferences, judgments, not perceptions, liable at any moment to be contradicted and proved false.

At present there is an immense amount of confusion in popular language, and even in scientific language, between propositions of these very different kinds, Almost any one would say in popular conversation, "Oh, you know that a cat has always four legs;" and few scientific writers would hesitate to say "we now know that the sun is about 92,000,000 of miles distant from the earth." Both statements are incorrect in calling that knowledge which is really belief. Probably a time will come in which greater precision of language will be demanded; when belief will be as clearly distinguished from knowledge as art now is from science.

Every student of science should cultivate such precision as one of his most precious instruments in the investigation of nature. For man's attempts to pick her locks are still supremely clumsy. He needs to make his keys a thousand times more delicate than any which he uses now before they will pass the wards of nature's inmost sanctuaries.

Not the least important respect wherein my map differs from the Government map is the much less area covered by Upper Keuper marl. The Geological Survey supposed that one effect of their two faults was to throw in between Lower Keuper a patch of Upper Keuper extending from Cranmer Street to Red Lane—that is, the space between the two faults. If their supposed curved fault had really existed I believe this would have been correct; but, as it is, the Upper Keuper, of which the Reservoir Hill consists, is cut off on the north side by No. 2 fault, and does not come in again till the ground rises to form Mapperley Hills. Then they mapped the Hunger Hills as being to a great extent composed of Upper Keuper. This is not so, however. The flat-topped appearance of these hills is caused, apparently, by a bed of sandstone, three or four feet thick, seen also in the cliff of Lower Keuper on Coppice New Road; and the Upper Keuper may be traced by the sudden rise of the ground,