The quantity of available coal yet remaining is, according to my own calculations, 24,000,000,000 tons. This is one-half the whole amount originally contained in the basin, a very large portion of which is at a depth below 4,000 and 5,000 feet. The produce of the 313 collieries in 1861 was 6,690,771 tons, which is considerably lower than in previous years, probably from the falling off in the export trade owing to the American war, but even should the amount reach ten millions of tons, there is enough to last 2,400 years, or to supply the whole consumption of Great Britain for about 300 years, -a fact which one might suppose ought to set the mind of the public at rest on the subject of our coal-resources.*

Cumberland Coal-field. This being detached from any of the above groups, I have reserved for the last. It forms a small band stretching along the sea, from Whitehaven to Maryport, and has been worked from very ancient times, as we have documents showing that the seams had been followed under the sea as early as the beginning of the 18th century. The area of the coal-field is 25 square miles, and the quantity of coal remaining for use is about 90 millions of tons.

The following summary of the above shall conclude this part of the subject.

The above figures being rendered into words, mean that there are in Great Britain, within a depth of 4,000 feet from the surface, 83,544,000,000 of tons of coal available, and that this quantity divided by the quantity raised in 1861, say 86,000,000 of tons, would last for about 970 years.

Having thus determined approximately the resources of our coalfields, and making no pretensions to prophecy, it might be wise, perhaps, to close this article without venturing one word regarding the future. Nothing is more liable to error than prospective statistics; the only person who is privileged to make use of them being the Chancellor of the Exchequer for the time being. At the same time, the falsifi

The estimates of Mr. Vivian are much larger than my own; but I think he has fallen into the error of multiplying the average thickness of coal into the full area; whereas the range of some seams is very far short of that.

The produce and number of colleries are from the Mineral Statistics of Great Britain,' for 1861, by R. Hunt, F.R.S., but differently arranged to suit the classification into groups here adopted.

VOL. I.

D

cations to which the estimates of this great functionary are often subject, may well be a warning to all would-be minor prophets not to venture on forbidden ground. We feel it, however, necessary to say a few words in vindication of what may appear the, somewhat arbitrary, limit of depth which we have adopted in the above calculations of our coal-resources. The reader will be justified in inquiring why we prefer 4,000 feet to 5,000 feet on the one hand, or 3,000 on the other, and he is therefore entitled to a reply, though it must be a brief one.

Taking the latter figure first, we may state at once that this depth has already been attained, or very nearly so, in more than one colliery, both in our own country and on the Continent,* and no colliery manager will maintain that the limit has been here reached.

With regard to 5,000 feet as a limit of depth the case is otherwise; for we have reason to conclude that supposing this depth to have been attained, the temperature, not to speak of other obstacles, would be found so high as to forbid the employment of human labour.

The increase of temperature as we penetrate from the surface, is a law which has been established on the evidence of a large number of observations in all parts of the world. In our own country very interesting and careful experiments have been made in several mines; both in the metallic mines of Cornwall, and the coal mines of the North of England. Having on a previous occasion given the experiments in detail, the results need only be stated here, and are summarized in the following table, together with the temperatures calculated to a depth of 4,000 feet.

In the above table "the temperature of no variation" adopted, is 50.5° at a depth of 50 feet from the surface.

From the foregoing tables it will be seen that even at a depth of 4,000 feet, a temperature may be expected more than tropical, though less than it would be at 5,000 feet, and sufficient, we think, to place

*One shaft in Belgium, we are assured, is 932 yards in depth. In Saxony, there is another upwards of 800 yards; and in the Dukinfield Colliery, the black mine has been followed to the depth of 940 yards from the surface.

+ Experiments made at Rose Bridge Colliery, Wigan, and Dukinfield Colliery, Ashton-under-Lyne, and detailed at length in the Coal-fields of Great Britain,' pp. 223-232. The latter were first published by Mr. W. Hopkins, F.R.S., in the Philosophical Transactions,' vol. cxlvii.

the limit of depth within the last-mentioned figure. The means by which the temperature even at 4,000 may be reduced so as to admit of healthful labour is ventilation, and the question remains, to what extent can this be accomplished. A series of interesting experiments undertaken at my request by Mr. Bryham, at Rose Bridge Colliery, Wigan, enables us to arrive at the following general conclusion:-that in a mine of ordinary extent, the temperature can be lowered by 20° or 30°, according to the distance from the shaft, and the season of the year. The cool air of winter reduces the heat of the mine more than that of summer time, so that even with a depth of 4,000 feet it may be often impossible to excavate the coal except during the colder months of the year.

Space will not admit of our doing more than to glance at the past history and future prospects of coal-mining. It may be said that up to the end of the last century, the art had only smouldered. It was when the invention of the steam-engine revolutionized the industry of this country, that mining burst forth with an energy previously unapproached. Probably not more than ten millions of tons of coal were raised at the commencement of this century; yet in 1830 the quantity raised was thirty millions, and in 1851 not less than fifty-four millions.* From 1854 downwards, we have the returns of the Mining Record Office,† which show a general tendency to expansion, though with fluctuations; the maximum having been reached in 1861, when the enormous quantity of eighty-six millions of tons was brought to the surface.

Notwithstanding these facts, however, it would be rash to assume that the experience of the past is to be a criterion of the future. We neither wish for, nor expect, an increase during the remainder of this century at all proportionate to that of the earlier half, and this view is borne out by some of the later returns. Some of our coal-fields, as has been shown, have passed their meridian, and, having expended their strength, are verging on decay. Others have attained their maximum, or nearly so; this indeed is the case with the majority. .The younger coal-fields will have much of their strength absorbed in compensating for the falling-off of the older; so that in a few years the whole of our coal-producing districts will reach a stage of activity beyond which they cannot advance, but around which they may oscillate. Entertaining these views, I am inclined to place the possible maximum of production at one hundred millions of tons a year; and yet it has been shown that even with this enormous "output," there is enough coal to last for eight centuries.

* On the authority of Mr. J. Dickinson, Her Majesty's Inspector of Coal Mines.

OCEANIC TELEGRAPHY.

I. THE DEEP-SEA BED OF THE ATLANTIC AND ITS INHABITANTS.

By Dr. G. C. WALLICH, F.L.S.

THE sounding-machine has already conducted us to the confines of an unexplored world. It has enabled us to penetrate the secret so long and so steadfastly concealed by nature beneath the waters of the ocean, by placing within our grasp the still living forms of creatures differing in no material respect from some of those inhabiting moderate depths, yet capable of sustaining existence under the extraordinary conditions known to prevail amidst the more profound abysses of the sea-bed. In short, it has taught us that our preconceived views concerning the incompatibility of these conditions with the performance of functions which are essential to life, are erroneous and demand most careful revision.

The fact, as thus stated, appears simple enough, and may, by many persons, be regarded as involving purely scientific issues. It will be our aim, however, to show that this is by no means the case; and that, whilst the interest attaching to the discovery of animal life under such circumstances is undoubtedly great, and likely to lead to valuable results in every department of Natural History, the practical bearing of this discovery on the question of Oceanic Telegraphy is of no less important a character. But in order to render ourselves intelligible, we must briefly direct attention to what was known on the subject prior to the time when it assumed its present aspect through the discovery of living star-fish procured from a depth of nearly a mile-anda-half below the surface.

Without stopping to notice the various conjectures regarding the nature of the deep-sea bed, which had previously been hazarded, it may suffice to mention that specimens of the material of which it is composed were, for the first time, systematically obtained about ten years ago. These consisted, for the most part, of an extremely fine mud, with a large proportion of microscopic shells belonging to one of the simplest forms of animal life with which we are acquainted. Some of the shells retained a considerable portion of the gelatinous substance of which the bodies of this class of organisms is composed. But at this point the evidence failed. For whilst the fact of these organisms having been raised from vast depths was too clearly established to admit of the slightest doubt, it is manifest that they might have been drifted from shallow water by oceanic currents, or have lived near the surface of the sea, and gradually subsided to the bottom after death. Accordingly, the mere presence of the gelatinous substance of which their bodies are formed, when taken in connection with the well-known preservative power of sea-water highly charged with saline matter, affords no proof whatever of the creatures having lived in the localities from which they had been conveyed by the sounding-machine. But although the determination of the question as to whether animal life can be sustained at such depths was reserved

for a later period, these earlier soundings were not barren of highly important results; for they enabled Professor Ehrenberg, on comparison of the material obtained from the bottom with that entering into the formation of chalk, to announce the extraordinary fact, that this rock is built up, atom by atom, of shells similar to those met with in such profusion along the bed of the ocean; and further, that it must have been deposited under conditions similar to those now prevailing; thereby furnishing the clearest proof that the great forces which were in operation at the sea-bed countless ages ago, are in operation still; and will, in all probability, continue to be so through all time.

We now arrive at the period when the survey of the sea-bed received a fresh and powerful impulse from the project of establishing communication between Europe and America by means of a Telegraphic Cable. With a view to ascertain the general contour and composition of the portion of the Atlantic it was proposed to traverse, an expedition was sent by the Government of the United States, to sound from shore to shore. But unfortunately, the information elicited in the course of this survey was so vitiated by inaccuracies as to have induced the eminent officer, then in charge of the Hydrographic department at Washington, to pronounce it untrustworthy. A second expedition was accordingly equipped, under the auspices of the British Government. Of the accuracy of the depths recorded on this occasion there could be no doubt. But the intervals between the positions at which soundings were taken were so great, and the means of obtaining specimens of the bottom so imperfect, that, looking at the matter as we now do after the event, it seems impossible to regard the information elicited as in any degree adequate to meet the requirements of the enterprise for which the survey was undertaken.*

It is true these soundings, as far as they went, indicated no extreme alternations of level along the course traversed. But on the other hand, nothing could be more hazardous than to assume, because a certain degree of uniformity as to depth manifests itself at the isolated spots on which soundings were taken, that a like degree of uniformity must prevail over the wide intervening spaces. Of the spaces themselves we know literally nothing. Nevertheless on these imperfect premises was it maintained, and by many persons believed, that the entire central tract of the Atlantic, instead of being characterized by variations of level and occasional areas of naked and perhaps rugged rock, such as we might expect to encounter here and there in a region so extended, consists of a level plateau, the entire surface of which is covered by a soft stratum of mud, similar to that indicated by the earlier soundings. Now, it must be obvious to every one that, however steep a submerged declivity may be, unless the depth is ascertained at two or more consecutive points, the information elicited will be the same as if the sounding-machine had been dropped on the most perfect level. And accordingly, for aught these soundings have shown to the

* To render this statement intelligible, it may be mentioned that along 1,300 miles of the Mid-Atlantic Telegraph route, only forty-one soundings were taken, the intervals varying between 32 and 71 geographical miles