Page images
PDF
EPUB

showers of rain, or is still further purified by the process of crystallization, and descends in snow. But since in falling through the atmosphere it imbibes the impurities which may happen to be present in this medium, (a process by which the purity of the atmosphere itself is maintained,) it is again subjected to filtration through the stratum of sand that covers the surface of the earth, and being thus separated from every impurity which it had either transported to the sea or accidentally imbibed on its return, it is restored to the earth to gush forth again in pure fountains, for the use of man. Since the rivers carry down saline matters to the

sea,

which they have dissolved in Howing on or under the earth, while by evaporation, in the returning system, water leaves all foreign ingredients behind, the ocean becomes permanently salt. It is not, however, certain that all the salt is thus supplied by the rivers. Since the different saline substances contained in river water are appropriated more or less in the marine structures that are constantly forming, as sea-shells and coral groves, it is not easy to determine whether the ocean was originally salt or has borrowed this quality entirely from the land. It amounts, at present, to about 31 per cent., and is nearly uniformly distributed over the globe, a proof that the waters of the ocean comîningle throughout their whole extent. The numerous currents which form so prominent an object of the work before us, keep its waters in continual circulation. No sooner is a portion of the equatorial seas heated, than it expands, and starts for the polar regions, and like portions of the polar waters commence their circuit to the

equator. This mutual exchange goes far to prevent excesses of heat on the one side, or of cold on the other, and contributes greatly towards diffusing a uniform temperature over the globe. Until recently these currents were little known, and it is chiefly by investigating their course and the laws that govern them, that the labors of Lieut. Maury and those who aid him in collecting materials for his Wind and Current Charts, have proved so useful to navigation, and will, as we believe, become, as they are improved and perfected by future researches, a still more signal benefit. Among these currents the Gulf Stream is the most remarkable, and that which has longest received the attention of both navigators and men of science. It is a hot sea river issuing from the Gulf of Mexico, where it has a temperature of 86 degrees. In the Straits of Florida its breath is 38 miles, but it widens as it advances northward, and attains a breadth of 75 miles off Cape Hatteras, and expands still more as it reaches the latitude of 'the Grand Banks, still preserving a temperature nearly

20 degrees above that of the neighboring seas. Its color (indi-
go blue) serves to distinguish its borders from the adjoining
waters, which are of a dark green hue; but the thermometer
is a still more definite guide to its exact limits, and shows that
its margin is exceedingly well defined, and that its waters
hardly inix at all with the cold and dense waters through
which it flows. These, indeed, on either hand, are like banks
to it, confining it like the banks of earth that form the margin
of an ordinary river. Since the bottom of the sea, as it ad-
vances to the north, grows more and more shallow, its breadth
of course expands, and thus the lower surface of the stream
presents an inclined plane rising in the direction of the stream;
and this is what Lieut. Maury means by the apparently para-
doxical expression, that “the Gulf Stream runs up hill." "The
amount of water kept in motion by this hot sea river is prodi-
gious, being, as our author supposes, 3,000 times as great as all
that the Mississippi pours into the Gulf of Mexico, and equal
to one-fourth of the entire water of the Atlantic; and since
whatever amount of fluid is withdrawn from the equatorial re-
gions and conveyed to the polar, must be replaced by a corres-
ponding amount in the opposite direction, he concludes that
the great current which descends from Baffin's Bay is no less
in amount than the Gulf Stream. This it meets near the Grand
Banks, where it divides into two portions, one crossing the
Gulf Stream at a considerable depth, where its course is de-
tected by the masses of ice which it bears along in its current,
and the other flowing down the coast, commonly at a great
depth, but occasionaly elevated by shoals almost to the surface
of the ocean, as at the Banks of Newfoundland, and at Cape
Hatteras. The Gulf Stream itself also divides into two parts
beyond the Banks, one portion running northward and flowing
along the western side of northern Europe, contributing greatly
to soften the rigors of those wintry climates, and the other
taking a sweep towards the Coast of Africa, and returning
again to the Gulf of Mexico to renew the same grand circuit.
The Gulf Stream retaining somewhat of the superior diurnal
velocity of the earth in the regions from which it flows, has an
easterly tendency as it proceeds towards the higher latitudes,
while the polar current, retaining somewhat of its inferior di-
urnal velocity, has a westerly tendency as it flows southward,
clinging closely to the main land. Its presence is recognized
even in the Carribean sea, where at a little depth the water is
found to be as cold as at the corresponding depth off the Arctic
shores of Spitzbergen.

[ocr errors]
[ocr errors]

What power can be assigned adequate to the movement of such a vast amount of water as that of the Gulf Stream? The cause usually assigned is the influence of the trade winds, which accumulate the waters of the Atlantic upon the great basin of the Gulf of Mexico. But our author considers the fact of such an elevation of the waters of this basin as is usually represented to take place, improbable, and maintains (what appears to us extremely probable) that the expansion of the waters of the equatorial seas, makes them flow off either way towards the poles, local circumstances determining them to run in particular channels, rather than in one unbroken wave; while the condensation of the cold waters of the polar seas, causes them in like manner to make their

make their way towards the equator,

The tendency of the waters of the middle portions of the Atlantic to join the great current that issues from the Gulf of Mexico, is strongly evinced by the following fact. It is a

a custom often practiced by sea-faring people, to throw bottles overboard, with a paper stating the time and place at which it is done. Lieut. Maury is in possession of a chart representing in this

way

the tracks of more than one hundred bottles. Of many thousands that have been cast into the sea, these are all that have been found and recorded. This chart indicates that the waters from every part of the Atlantic tend towards the Gulf of Mexico and its stream. Bottles cast into the sea midway between the old and new worlds, near the coasts of Europe, Africa, and America, at the extreme north and farthest south, have been found either in the West Indies, or within the wellknown range of the Gulf Stream.

Besides the immense aid which these researches promise to lend to the navigators of the ocean, they will also contribute vastly to promote the discovery and acquisition of its hidden treasures. Already the tracing of warm and cold currents has opened new retreats of the sperm whale, which lives only in warm water, and brought to light new homes of the right whale, which is the tenant only of cold water, and never crosses the torrid zone. So great indeed is the importance of the whale fishery to the United States, that our author, with an excusable degree of enthusiasm, pronounces it to be a source of wealth transcending all the mines of California.

ART. VIII.--RECENT WORKS ON PSYCHOLOGY.

The Elements of Intellectual Philosophy. By Francis WAYLAND, President of Brown University, and Professor of Moral and Intellectual Philosophy. (12mo. pp. 426.) Boston:

Phillips, Sampson & Co., 1854. Empirical Psychology; or, The Human Mind as given in Con

sciousness. By LAURENS P. HICKOCK, D. D., Union College.

(12mo. pp. 400.) Schenectady: G. Y. Vandebogert, 1851. A System of Intellectual Philosophy. By Rev. Asa MAHAN,

first President of Cleveland University. Revised and enlarged from the second edition. (12mo. pp. 476.) New York: A. S. Barnes & Co., 1854.

The appearance of three new text-books on Psychology, at nearly the same time, is an event of not a little significance for American science. We call all of these works new, for the second edition of Mahan's treatise is so much changed and improved, as to deserve to be called a new work. Text-books in this department of knowledge have rarely been prepared in this country, and still more rarely in England, and the want of a good mannal has been seriously felt by instructors on both sides the ocean.

A brief and critical examination of the works before us as to their philosophical merits, and their fitness for the object for which they were prepared, will not be inappropriate to our journal.

We are struck, at the outset, with the somewhat significant fact, that these three text-books are written in the spirit of three different schools of philosophy—not narrowly nor confessedly, but still really and strikingly. Dr. Wayland represents the Scotch school of Reid, as modified by Sir William Hamilton, with a somewhat liberal indebtedness to Cousin. Dr. Hickock is German, or rather Kantian, in his terminology and his distinctions, without adopting Kant's extreme and sceptical dogmas. Mr. Mahan is an eclectic, being more decidedly a follower and imitator of Cousin. His eclecticism degenerates sometimes into the merely aggregative, and he delights occasionally in strange and incongruous combinations from Kant, Coleridge, Cousin, and himself, but showing here and there great vigor and acuteness, and very considerable philosophical ability.

9

VOL. XIII.

Dr. Wayland deserves first to be considered, as he is the oldest man, and the oldest teacher of the three; as he is the author of a Moral Philosophy which has had an extensive sale, and is also the Professor of Intellectual Philosophy in an institution, which, under his guidance and authority as president, proposes to teach these higher branches of study more thorough Iy and philosophically than the other American colleges. flis text-book was prepared in and for the lecture-room, which is the best, and indeed the only place, from which a text-book should ever proceed. It has also been matured by the thought and experience of a score of years.

The style of this book is plain and intelligible. The sentences are short and simple. Whatever the author desires to say, he

says distinctly. He can be followed with ease by the reader or student. Šis illustrations are numerous; if they are sometimes homely and superfluous, they will be valued by many who like easy reading, in a book of this kind. The practical remarks are just, sometimes they are weighty. When they are common-place, they are always designed to be useful. The book is, in short, just what we should have looked for, intelligible in style, clear in thought, and as full as could be expected from a limited range of reading, and as acute from one who seems to have reproduced the thoughts of his teachers, so far as was required, to satisfy himself and his pupils, with an instructive and useful course of lectures. He seems, however, not to have recast these thoughts in a method or an order peculiarly his own-nor to have rigidly demonstrated and indicated their truth, nor to have aimed to make them eminently and severely the means of a philosophical discipline to his pupils. It is principally by thus recasting these truths that the teacher of mental philosophy can be original or eminently useful. The truths which he imparts are many of them undisputed and common-place. They must become in some way fresh and new. If the teacher seeks to make them so by becoming too refined and subtle for the majority of his pupils, he involves them in a maze, through which they grope in perplexity at themselves, and in stupid wonder at their teacher, and end with a deadly aversion to metaphysics. Or, if the teacher pursues the too common method of presupposing that his pupils are competent to decide upon the loftiest questions in metaphysics without having studied its elements, he may soar with them till they together reach an atmosphere too thin to sustain even the selfconceit which inflates both the teacher and the taught. But it he does not give distinct conceptions, and insist on precise definitions, and bind one truth to another, in a rigid and scientific

« PreviousContinue »