had been observed, viz., that in by far the greater number of crystallized substances, which possess the property of double refraction, neither of the images follows the ordinary law, but both undergo a deviation from the original plane. Now, this had never been observed in any previous trial, and all opinion was against it. But when put to the test of experimeut in a great variety of new and ingenious methods, it was found to be fully verified and to complete the evidence, the substances on whose imperfect examination the first erroneous conclusion was founded, having been lately subjected to a fresh and more scrupulous examination, the result has shewn the insufficiency of the former measurements, and proved in perfect accordance with the newly discovered laws. Now, it will be observed in this case, first, that so far from the principles assumed by M. Fresnel being at all obvious, they are extremely remote from ordinary observation and, secondly, that the chain of reasoning by which they are brought to the test, is one of such length and complexity, and the purely mathematical difficulty of their application so great, that no mere good common sense, no general tact or ordinary practical reasoning, would afford the slightest chance of threading their mazes. Cases like this are the triumph of theories. They shew at once how large a part pure reason has to perform in our examination of nature, and how implicit our reliance ought to be on that powerful and methodical system of rules and processes, which constitute the modern mathematical analysis, in all the more difficult applications of exact calculations to her phenomena.

'To take an instance more within ordinary apprehension. An eminent living geometer has proved, by calculations founded on strict optical principles, that in the centre of the shadow of a small circular plate of metal, exposed in a dark room to a beam of light emanating from a very small brilliant point, there ought to be no darkness, in fact, no shadow at that place; but on the contrary, a degree of illumination precisely as bright as if the metal plate were away. Strange and even impossible as this conclusion may seem, it has been put to the trial, and found perfectly correct.' ―pp. 30-34.

The manner in which the laws of nature become opponents of human exertion on the one hand, and its irresistible auxiliaries on the other, is thus curiously elucidated.

If the laws of nature, on the one hand, are invincible opponents, on the other, they are irresistible auxiliaries; and it will not be amiss if we regard them in each of those characters, and consider the great importance of a knowledge of them to mankind,

I. In showing us how to avoid attempting impossibilities.

II. In securing us from important mistakes in attempting what is, in itself, possible, by means either inadequate, or actually opposed, to the end in view.

'III. In enabling us to accomplish our ends in the easiest, shortest, most economical, and most effectual manner.

IV. In adducing us to attempt, and enabling us to accomplish, objects which, but for such knowledge, we should never have thought of undertaking.

'We shall therefore proceed to illustrate by examples the effect of physical knowledge under each of those heads.

'Ex. 1. It is not many years since an attempt was made to establish a colliery at Bexhill, in Sussex. The appearance of thin seams and sheets of fossilwood and wood-coal, with some other indications similar to what occur in the neighbourhood of the great coal-beds in the north of England, having led to the sinking of a shaft, and the erection of machinery on a scale of vast expense, not less than eighty thousand pounds are said to have been laid out on this project, which, it is almost needless to add, proved completely abortive, as every geologist would have at once declared it must, the whole assemblage of geological facts being adverse to the existence of a regular coal-bed in the Hastings' sand; while this, on which Bexhill is situated, is separated from the coal-strata by a series of interposed beds of such enormous thickness as to render all idea of penetrating through them absurd. The history of mining operations is full of similar cases where a very moderate acquaintance with the usual order of nature, to say nothing of theoretical views, would have saved many a sanguine adventurer from utter ruiu.

Ex. 2. The smelting of iron requires the application of the most violent heat that can be raised, and is commonly performed in tall furnaces, urged by great iron bellows driven by steam-engines. Instead of employing this power to force air into the furnace through the intervention of bellows, it was, on one occasion, attempted to employ the steam itself, in, apparently, a much less circuitous manner; viz. by directing the current of steam in a violent blast, from the boiler at once into the fire. From one of the known ingredients of steam being a highly inflammable body, and the other that essential part of the air which supports combustion, it was imagined that this would have the effect of increasing the fire to tenfold fury, whereas it simply blew it out; a result which a slight consideration of the laws of chemical combination, and the state in which the ingredient elements exist in steam, would have enabled any one to predict without a trial.

Ex. 3. After the invention of the diving-bell, and its success in subaqueous processes, it was considered highly desirable to devise some means of remaining for any length of time under water, and rising at pleasure without assistance, so as either to examine, at leisure, the bottom, or perform, at ease, any work that may be required. Some years ago, an ingenious individual proposed a project by which this end was to be accomplished. It consisted in sinking the hull of a ship made quite water-tight, with the decks and sides strongly supported by shores, and the only entry secured by a stout trap-door, in such a manner, that by disengaging, from within, the weights employed to sink it, it might rise of itself to the surface. To render the trial more satisfactory, and the result more striking, the projector himself made the first essay. It was agreed that he should sink in twenty fathoms water, and rise again without assistance, at the expiration of twenty-four hours. Accordingly, making all secure, fastening down his trap-door, and provided with all necessaries, as well as with the means of making signals to indicate his situation, this unhappy victim of his own ingenuity entered and was sunk. No signal was given, and the time appointed elapsed. An immense concourse of people had assembled to witness his rising, but in vain; for the vessel was never seen more. pressure of the water at so great a depth had, no doubt, been completely under-estimated, and the sides of the vessel being at once crushed in, the unfortunate projector perished before he could even make the signal concerted to indicate his distress.

The

Ex. 4. In the granite quarries near Seringapatam, the most enormous blocks are separated from the solid rock by the following neat and simple process. The workman having found a portion of the rock sufficiently extensive, and situated near the edge of the part already quarried, lays bare the upper surface, and marks into a line in the direction of the intended separation, along which a groove is cut with a chisel, about a couple of inches in depth. Above this groove a narrow line of fire is then kindled, and maintained till the rock below is thoroughly heated, immediately on which a line of men and women, each provided with a pot full of cold water, suddenly sweep off the ashes, and pours the water into the heated groove, when the rock at once splits with a clean fracture. Square blocks of six feet in the side, and upwards of eighty feet in length, are sometimes detached by this method, or by another equally simple and efficacious, but not easily explained without entering into particulars of mineralogical detail.

Ex. 5. Hardly less simple and efficacious is the process used in some parts of France, where mill-stones are made. When a mass of stone sufficiently large is found, it is cut into a cylinder several feet high, and the question then arises how to subdivide this into horizontal pieces so as to make as many mill-stones. For this purpose horizontal indentations or grooves are chiselled out quite round the cylinder, at distances corresponding to the thickness intended to be given to the mill-stones, into which wedges of dried wood are driven. These are then wetted, or exposed to the night dew, and next morning the different pieces are found separated from each other by the expansion of the wood, consequent on its absorption of moisture; an irresistible natural power thus accomplishing, almost without any trouble, and at no expense, an operation which, from the peculiar hardness and texture of the stone, would otherwise be impracticable but by the most powerful machinery or the most persevering labour.'-pp. 44—48.

Mr. Herschel concludes the first part of his discourse with the following peroration, in which the philosopher exalts so nobly the politician.

Finally, the improvement effected in the condition of mankind by advances in physical science, as applied to the useful purposes of life, is very far from being limited to their direct consequences in the more abundant supply of our physical wants, and the increase of our comforts. Great as these benefits are, they are yet but steps to others of a still higher kind. The successful results of our experiments and reasonings in natural philosophy, and the incalculable advantages which experience, systematically consulted and dispassionately reasoned on, has conferred in matters purely physical, tend of necessity to impress something of the well-weighed and progressive character of science on the more complicated conduct of our social and moral relations. It is thus that legislation and politics become gradually regarded as experimental sciences; and history, not, as formerly, the mere record of tyrannies and slaughters, which, by immortalizing the execrable actions of one age, perpetuates the ambition of committing them in every succeeding one, but as the archive of experiments, successful and unsuccessful, gradually accumulating towards the solution of the grand problem-how the advantages of government are to be secured with the least possible inconvenience to the governed. The celebrated

apophthegm, that nations never profit by experience, becomes yearly more and more untrue. Political economy, at least, is found to have sound principles, founded in the moral and physical nature of man, which, however lost sight of in particular measures-however even temporarily controverted and borne down by clamour-have yet a stronger and stronger testimony borne to them in each succeeding generation, by which they must, sooner or later, prevail. The idea once conceived and verified, that great and noble ends are to be achieved, by which the condition of the whole human species shall be permanently bettered, by bringing into exercise a sufficient quantity of sober thought, and by a proper adaptation of means, is of itself sufficient to set us earnestly on reflecting what ends are truly great and noble, either in themselves, or as conducive to others of a still loftier character; because we are not now, as heretofore, hopeless of attaining them. It is not now equally harmless and insignificant, whether we are right or wrong; since we are no longer supinely and helplessly carried down the stream of events, but feel ourselves capable of buffetting at least with its waves, and perhaps of riding triumphantly over them: for why should we despair that the reason which has enabled us to subdue all nature to our purposes, should (if permitted and assisted by the providence of God) achieve a far more difficult conquest; and ultimately find some means of enabling the collective wisdom of mankind to bear down those obstacles which individual short-sightedness, selfishness, and passion, oppose to all improvements, and by which the highest hopes are continually blighted, and the fairest prospects marred.'-pp. 72-74.

In the second portion of his work, Mr. Herschel enters into a detailed consideration of the principles that are to be adopted in pursuing researches in physical science. He lays down the most approved rules, for practically carrying on this examination of nature and he shows the propriety, and, indeed, the necessity of these rules, by adverting to the instances of their successful application. This division of the volume is deeply important, and it embraces matter of use and interest for every votary of science whatever be the branch of study he pursues. The third part is devoted to a view of the subdivision of the physical sciences, which are all separately considered, and their reciprocal influence pointed out. The whole is, indeed, as to plan and execution, a master-piece, that reflects the highest honour on the author, not less as a philosopher than as a man.

Perhaps we could not better shew the respect we entertain for Mr. Herschel's talents, than by pointing out some drawbacks to the pleasure we have received in perusing this volume, and which we are disposed to do the more, because we have no doubt of many opportunities being given to Mr. Herschel to correct this discourse. Portions of the work are not so carefully written as to be easily intelligible to all readers. Some of the sentences are rather too much involved--the relatives and antecedents are sometimes crowded together so thickly in the same period, as that a reader must be pretty expert of apprehension who can, without some hesitation, make a correct distribution of the affinities in it. To

say that Mr. Herschel was always perfect in his definitions too, would be awarding a degree of praise which, it is doubtful, if human fallibility will ever allow any man to deserve. For example, he begins the second chapter of his work in these words :

:

⚫ Science is the knowledge of many, orderly and methodically digested and arranged, so as to become attainable by one. The knowledge of reasons and their conclusions constitutes abstract, that of causes and their effects, and of the laws of nature, natural science.'—p. 18.

This definition seems to be a very singular one, for it makes it necessary that a discovery, in order to become a part of science, must be known to many first. Thus Newton's theory of gravitation could not have been admitted to be science, until the accident of its communication to many persons. One would think, that when Newton found it out, it was as much science as ever, and remained so during the time that it was known only to himself.The second sentence of the above passage is, as it seems to us, wholly inadequate to express the exact meaning of Abstract Science. It consists, not only of the knowledge of reasons and conclusions, but of reasons and conclusions drawn from the contemplation of ideas, having no reference to objects or circumstances, but perfectly abstracted from such.

But there are spots on the sun, and perhaps it is only in the policy of a wise Providence that they are placed there to check the excessive splendour of a luminary, which would otherwise be too powerful for our feeble senses.

ART. XII.-Report of the Commissioners for the Herring Fishery of their Proceedings for the Year ended 5th April, 1830. Printed by Order of Parliament. 1830.

THE cessation of the bounty for the encouragement of the fishery having taken place in April, 1830, it may not be useless to direct the public attention to the state of this branch of national industry, in order that we may learn, as much as we can, from experience, what has been the effect of such of the theories of political economy as have been already reduced to practice. It appears from the Report before us, that there were cured in the year ended April, 1830,329,557 barrels of white herrings-being a decrease, as compared with the number cured in the former year, of 26,422 barrels. The quantity of cod and ling cured in the last year has increased-it amounting to 104,914 cwts. cured dried--and 5,652 cwts., and 8,836 barrels cured in pickle.

From the boat account it appears that 11,199 boats were employed in the shore-curing department of the fishery, manned by 48,699 fishermen, and the total number of persons employed therein was 80,300.