where these beds throw out springs of water. Whole lines of such springs coinciding with the bottom of coalbeds can be traced in the hilly coal districts of South Wales and Monmouthshire, and often on a hill side faults traversing the general mass can be as well seen, where these lines are interrupted, as if a diagram section were before us.

In some of the beds immediately subjacent to the coal peculiar fossil plants are found. In the palæozoic coal of the British Islands a fossil plant, named Stigmaria ficoides, is very characteristic. Peculiar fossil plants, not the one mentioned, are discovered, it is thought, well marking the beds on which the coal-beds rest in the Burdwan coal district in India, and other instances of a similar kind are recorded. It will be obvious that, although the conditions for the production of marked accumulations may have preceded the growth of most of the coal-vegetables themselves, the latter may not have sometimes grown, so that no coal rests upon such beds, a fact observed, and according to conditions more in one part of a coal district than in another. Still these beds, when any such occur, are useful to trace, since while we find in one locality no vegetable accumulation to have taken place upon them, or if effected the vegetable matter to have been subsequently removed, upon an extension of the same beds we may often see good workable coal.

Though in cliffs, either on the shore or on the sides of rivers, hills, and mountains, we commonly find the most direct evidence of the existence of coal, it may be often traced to its beds, where such occur, by means of the detritus brought down by brooks and rivers. By following rolled pebbles up such water-courses they

may be often seen to end near some bed or beds whence they have been derived. If these cross the stream, a good opportunity may be afforded for examining their quality and thickness. The pebbles may, however, come from the sides of some adjacent hills sloping towards the streams, the beds of coal not crossing them, fragments only of their outcrop being mingled with any others of associated beds. The thickness of such coal-beds may be thus concealed, as will be readily seen by the annexed section, in which a represents the river course, up which pebbles of coal may be traced; bb beds of coal, the out-crops of which, c c, may be much concealed by fragments of rock descended

d

d

2

from above and mingled in a fragmentary covering dd. The best should be done to obtain a knowledge of the associated beds by tracing up the rills of water descending the sides of the hills. Excellent evidence may thus be often obtained, and the true position of the coalbeds found. In selecting specimens of coal in such cases, it rarely happens that a portion of it can be procured fairly exhibiting its qualities, injury having arisen from atmospheric influences. If the out crop of the coal can be attained, it is always desirable to penetrate as far as circumstances will permit into the body of

the bed, thence selecting a fair specimen. When this cannot be done, and a voyager often has but little time for his researches, fragments lying about should be selected which may appear the least decomposed, and if these be different qualities, as if of portions of different beds, they also should receive attention. In all cases where fossil plants are mingled with the coal or associated beds, specimens as various as can be obtained should be secured. These have a geological bearing which may often turn out of great practical importance in some given region.

It scarcely requires remark that the foregoing observations are but hints which it is hoped may be useful to those engaged in voyages of discovery and survey, or who, on more general service, may feel inclined, whenever fitting opportunities may present themselves, to devote some portion of the time not occupied by their professional duties to the study of minerals, either for purely scientific purposes, for their useful employment, or for both combined. That these opportunities do present themselves we well know, or rather if sought will be found more frequently than might be imagined. Many a walk along a coast may thus be advantageously turned to account, and an interest be excited not at first thought probable. Not only may a naval man thus add to his own stock of knowledge, but he may most materially by his exertions promote the advance of science and its applications generally, minerals being objects of great interest, whether we regard them with reference to their importance to man, and the aid many of them afford to the spread of civilization, or as connected with several sciences, even those of the highest order.

SECTION IX.

METEOROLOGY.

BY THE EDITOR.

THERE is no branch of physical science which can be advanced more materially by observations made during sea voyages than meteorology, and that for several distinct reasons. 1st. That the number and variety of the disturbing influences at sea are much less than on land, by reason of the uniform level and homogeneous nature of its surface. 2ndly. Because, owing to the penetrability of water by radiant heat, and the perpetual agitation and intermixture of its superficial strata, its changes of temperature are neither so extensive nor so sudden as those of the land. 3rdly. Because the area of the sea so far exceeds that of the land, and is so infinitely more accessible in every part, that a much wider field of observation is laid open, calculated thereby to afford a far more extensive basis for the deduction of general conclusions. 4thly. The sea being the origin from which all land waters are derived, in studying the hygrometrical conditions of the sea atmosphere, we approach the chief problems of hygrology in their least involved and complicated form, unmixed with those considerations which the perpetually varying state of the land (as the recipient at

uncertain intervals of derivative moisture) forces on the notice of the meteorologist of the continents. Nor ought it to be left out of consideration that this, of all branches of physical knowledge, being that on which the success of voyages and the safety of voyagers are most immediately and unceasingly dependent, a personal interest of the most direct kind is infused into its pursuit at sea, greatly tending to relieve the irksomeness of continued observations, to insure precision in their registry, and to make their partial or complete reduction during the voyage an agreeable, as it always is a desirable object.

It happens fortunately, that almost every datum which the scientific meteorologist can require is furnished in its best and most available state by that definite, systematic process, known as the "keeping a meteorological register," which consists in noting at stated hours of every day the readings of all the meteorological instruments at command, as well as all such facts or indications of wind and weather as are susceptible of being definitely described and estimated without instrumental aid. Occasional observations apply to occasional and remarkable phenomena, and are by no means to be neglected; but it is to the regular meteorological register, steadily and perseveringly kept throughout the whole of every voyage, that we must look for the development of the great laws of this science. The following general rules and precautions are necessary to be observed in keeping such a register:

1. Interruptions in the continuity of observations by changes of the instruments themselves, or of their adjustments, places, exposure, mode of fixing, reading, and registering, &c., are exceedingly objectionable,