the shores of Asia," towards the Aleutian Islands, tempering climates, and losing itself on its way to the north-west coast of America.

It has been long ago ascertained, that while there is a surface current from the Atlantic always running into the Mediterranean, there is an outward under-current running into the Atlantic, and charged with the additional salt produced by evaporation from the inland sea. This opinion of our author has been controverted by Admiral Smyth and Sir Charles Lyell, from the fact that water taken fifty miles within the Straits, from a depth of 4020 feet, was found by Dr. Wollaston to be four times salter than common sea water, combined with the fact that the greatest depth of water at the Straits is 1320 feet. Hence they conclude that water, lying at depths greater than 1320 feet, can never flow out into the Atlantic over the submarine barrier at the Straits. Lieut. Maury is at much pains to refute this apparently formidable objection to his theory, but he required only to refer to the beautiful experiments of Venturi on the lateral communication of motion in fluids from which it is proved that a current of pure water passing over a deep pool of ink, or any other fluid colored on purpose, would soon empty the pool, and replace the ink or colored fluid with the pure water of the current. Hence it is manifest that the brine or very salt water which may occupy the depths or cavities of the Mediterranean Sea must be carried out into the Atlantic. Owing to the high temperature of the Indian Ocean, large currents of warm water have their origin there. One of these is the Mozambique or Lagullas current. Another, escaping through the Straits of Malacca, and joined by others from the Java and China

After treating of the currents in the Pacific, of Humboldt's current on the coast of Peru, of under-currents and the currents in the Atlantic, Lieutenant Maury proceeds to discuss the very interesting subject of "The open sea in the Arctic Ocean." Dr. Scoresby informs us that whales have been caught near Behring's Straits with harpoons in them belonging to ships known to cruise in Baffin's Bay; and as it has been ascertained that these whales could not have passed round Cape Horn or the Cape of Good Hope, it follows that they must have traveled in open water through the Arctic Sea. As an additional argument for an open sea near the Pole, our author mentions the existence of a warm under-current from the Atlantic into the Arctic Ocean through Davis's Straits, and he adds the opinions of Lieutenant De Haven, Captain Penny, and Dr. Kane,* who found an open sea in very high latitudes. Important as these arguments are, the existence of an open sea at the North Pole itself may be inferred from the existence of two poles of maximum cold surrounded by isothermal lines indicating increasing temperatures as we approach the Pole along the cold meridians which pass through the poles of cold, and the pole of revolution.

The influence of the saltness of the sea on the equilibrium of its waters is the subject of Lieutenant Maury's ninth chapter. We have already seen that, owing to evaporation from its surface, which increases the saltness of the sea in certain places, and to the introduction of large rivers of fresh water, and heavy falls of rain, which diminishes its saltness in others, it must have various degrees of saltness in different localities. The currents, however, which we have described as in the waters which have different degrees of saltness, produce sea water of a uniform degree of saltness; so that "the constituents of sea water are, generally speaking, as constant in their proportions as are the components of the atmosphere." In order to explain why the sea is salt and

* See this Journal, vol. xxvi., pp. 228, 229, 236.

not fresh, Lieutenant Maury suggests that one of its purposes was to impart to its waters the forces and powers necessary to make their circulation as complete," and "as perfect as is that of the atmosphere or blood." In support of his opinion, that the sea has a system of circulation for its waters, our author refers to the coral islands, reefs, beds, and atolls of the Pacific, built up with materials quarried, as he expresses it, by a certain kind of insect from sea water, which contains 3 per cent of solid matter supplied by rivers, in the form of common salt, sulphate and carbonate of lime, magnesia, soda, potash, and iron. If fresh supplies of these materials were not obtained by currents, the little creatures that build the coral rocks would perish for want of food before their work was finished.

Did the sea consist of fresh water, a feeble system of circulation would be produced by heat and evaporation alone, excluding the influence of the winds. Surface currents of warm and light water would from the Equator to the Pole, pass and another set of under-currents, of cooler, dense, and heavy water, would pass from the Poles towards the Equator. But if the sea consisted of salt water, which contracts as its temperature is lowered till it reaches 28°, a new force is called into play. Evaporation in the tradewind region lowers the sea level, and increases the saltness of the sea. The water thus heavier sinks, while the lighter water rises, producing a vertical circulation. The raised vapor, carried by the currents of air to colder regions, gives to the ocean more fresh water as rain, or snow, than it returns to the atmosphere as vapor. The sea level is thus raised, and being depressed in the evaporating regions, a system of surface currents, moved by gravity alone, passes from the Poles towards the Equator.

If the sea had not been salt from "the beginning, "there would have been none of the sea-shells that cover the top of the Andes, or those infusorial deposits which astonish us by their magnitude and extent, and none of the coral islands which adorn the Pacific. When the rains dissolve the salts of the earth, and the rivers carry them to the sea, the marine insects elaborate them into pearls, shells, and corals; and while they are preserving the purity of the sea, they assist in the regulation of

climates in parts of the earth far removed from the spots where they dwell.

Without entering into the question, whence does the sea derive its saltnesswhether, according to Darwin, from the washings of rains and rivers, or, as Lieutenant Maury believes, from the Almighty's fiat on the morning of the creation-it is interesting to notice the quantity of solid matter, in the form of salts, which the sea holds in solution. Taking the average depth of the ocean at two miles, and its average saline strength at three and a half per cent, its salt would cover, to the thickness of one mile, an area of seven millions of square miles, all of which passes into the interstices of sea water without increasing its bulk.

In a short chapter on "The Equatorial Cloud Ring," illustrated by his “Diagram of the Winds," we have the terraqueous globe divided into nine portions.

1. The Equatorial Cloud Ring, or the Belt of Equatorial Calms and Rains, or the Equatorial "Doldrums" of the sailor a word which we hope will from escape future treatises on the sea.

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the

2. The North-East Trade-Winds. 3. The Calm Belt of Cancer "Horse Latitudes " of the sailor. 4. The prevailing winds from the Equator towards the North Pole. 5. The North Polar Calms. 6. The South-East Trade-Winds. 7. The Calm Belt of Capricorn. 8. The prevailing winds from the Equator towards the South Pole.

9. The South Polar Calms. The Equatorial Calm Belt is not only the region of calms and baffling winds, but also of rains and clouds; and under its dense, close, and sultry atmosphere, the Australian emigrants find it a "frightful graveyard" for children and delicate passengers. Under this cloud ring, which encircles the earth, the thermometer and barometer stand lower than in the clear weather on either side of it. In the parallels over which it hangs, it promotes the precipitation of rain at certain periods; and "by traveling with the calm belt of the Equator to the north or south, it shifts the surface from which the heating rays of the sun are to be excluded, and gives a tone to the atmospherical circulation of the world, and a vigor to its vege tation." When it has thus left the Equator, the rays of a vertical "torrid sun”

scorch the earth. Plants wither. Animals die. The mitigating cloud ring returns, and the burning rays of the sun are no longer received on the surface of the earth, but upon the upper surface of the cloud belt. Under this heating influence the clouds "melt away and become invisible;" the sun's rays dissolving one set of elevations, and creating another set of depressions. Were this cloud ring luminous, and seen from one of the planets, it would, according to Lieut. Maury, resemble the Ring of Saturn, the side which is opposite us appearing "jagged, rough, and uneven;" and it would seem to have a motion contrary to that of the earth.

In exploring the physical geography of the sea, our author accompanies the geologist far away from the sea-shore" to study the phenomena presented by the inland basins of the earth, the Dead Sea, the Caspian, the Lake of Aral, etc., which have no sea drainage, and he proposes to explain their present condition by what he calls "the geological agency of the winds." The Dead Sea, the most interesting of these basins, is 1500 feet beneath the general sea level of the earth. The geologist refers this remarkable depression to forces of elevation or subsidence which have resided in the vicinity of the basin; but Lieut. Maury supposes, and endeavors to show, that these forces have come from the sea in the other hemisphere, through the agency of the winds. He supposes that the amount of precipitation (of rain, snow, dew, etc.) upon the water-shed of the Dead Sea, etc., was, at some former period greater than its present annual amount of evaporation, and he asks, from what part of the sea did that excess of vapor come? and what has cut off that supply, since the amount of evaporation is equal to that of precipitation, and the level of this and other rock seas is as permanent as that of the ocean? If the Dead Sea formerly sent a river to the ocean, it would carry off the excess of precipitation over the vapor raised, and carried away by the winds. According to our author, "the salt-beds, the watermarks, the geological formations, and other facts traced upon the tablets of the rocks, indicate plainly that the Dead Sea and the Caspian had upon them in former periods more abundant rains than they now have;" and he is of opinion that the supply has not been cut off by the eleva

tion or depression of the Dead Sea basin, and that the upheaval of mountain ranges and continents across the course of the winds has, by means of the winds produced upon inland lakes, the effect which would be occasioned by a greater or less amount of moisture.

As an example of drainage that has been cut off, and an illustration of the process by which precipitation and evaporation are equalized, our author takes the case of the Salt Lake of Utah, the basin of which is now salting up, and from which there is said to be the appearance of an old channel which once conducted its waters to the sea. If such a river existed, some cause must have operated to stop the supply of moisture, the excess of which was carried off by the river. Our author conceives that if the Sierra Nevada, the mountains to the west of the lake, now stand higher than they formerly did, and if the winds which fed the Salt Lake valley with moisture had to pass over the mountains, a less quantity of vapor would be carried across them than when the summit of the range was lower and warmer. In like manner, our author supposes that the Dead Sea, and the great inland basins of Asia, may have been deprived of the vapor which they once received when they were emptied by rivers into the sea, by the elevation of the South-American continent, and the upheaval of its mountains. The elevation of the Andes has thus made Western Peru a rainless country, and Atacama a desert, by stopping the vapors of the ocean which fed them with moisture; and in the opinion of Lieutenant Maury, who adduces various ingenious arguments in support of it, it is the influence of the same range that has depressed the waters of the inland basins of Asia. According to geological speculations, the upheaval of one continent is supposed to be accompanied by the depression of another, as exhibited in the islands of the Pacific; and therefore, if we adopt the views of our author, we must take it for granted that no continent was depressed to the west of the Dead Sea when South-America rose from the ocean. If the winds have the geological agencies now ascribed to them, our author conceives that they may instruct us in the chronology of geological events which have taken place in different hemispheres, "telling us which be the older-the Andes watching

Having thus succeeded in reaching the bottom of the sea, an additional contrivance was required to bring up specimens of the materials of which it was composed, This was accomplished by Mr. Brooke, of the U. S. Navy, by means of his "Deep Sea Sounding Apparatus." At the end of the tubular iron rod which passes through the cannon ball sinker, is placed a cup containing a little soap or tallow, called arming, to which the specimens of the sea-bottom adhere, and are brought up, after the ball has been detached from the rod. By means of this apparatus, specimens have been obtained from depths of more than three miles-some from the Coral Sea of the Indian Archipelago, and some from the Pacific and Atlantic Oceans. Among the sea basins of the ocean, that of the Atlantic, the most frequented, has a peculiar interest, and is the subject of a long and interesting chapter in the "Geography of the Sea." Lieut. Maury has given us an orographic projection of its bottom, in which the soundings are represented by four different degrees of shade. The darkest, which is nearest the shore line, indicating depths less than 6000 feet; the next, those less than 12,000 feet; the third, those less than 18,000 feet; and the fourth, or lightest, those not greater than 24,000 feet. From the blank space north of Nova Scotia and the Grand Banks of Newfoundland, very deep water has been reported. The deepest part is probably between the Bermuda Isles and the Grand Banks. In another plate Lieut. Maury has given a vertical section of the Atlantic, showing the contrasts of its bottom with the sea-level in a line from Mexico, across Yucatan, Cuba, San Domingo, and the Cape de Verd Islands, to a point in the coast of Africa, in the parallel of 16° of north latitude. The importance of this system of deep-sea sounding has been recently impressed upon the public mind, and may be regarded as one of the many proofs constantly presenting themselves, that there is no branch of physical knowledge which will not sooner or later find a practical and social application. In the soundings of the NorthAtlantic Ocean, the bold engineer who has faith in the resources of science, has seen the practicability of laying a cable

a distance of one thousand six hundred and forty miles! Between these capes there is a remarkable steppe or ridge, already known as the Telegraphic Plateau, above which there is not more than 10,000 or 12,000 feet, or two miles of water. A company of enterprising and wealthy individuals has already been organized to carry a submarine cable across this plateau, and they have made a contract with a party in England to deliver to them in June, 1858, a telegraphic cable of the required length; and, notwithstanding the failure of their first attempt, we can not doubt that it will be ultimately successful.

In connection with this elevated ridge across the Atlantic, there is a ridge on the land "which runs nearly, if not entirely, around the earth." Leaving America between 45° and 50° N., it includes Great Britain, separates the drainage of the Arctic Ocean from the drainage southwards, and forms a chain of steppes and mountains extending across the continent of Asia, and disappearing in the Pacific. It was in the subaqueous part of the ridge that Brooke's sounding apparatus brought up calcareous shells of the Foraminiferæ, while in the Coral Sea the silicious infusoria and the Polythalamia were obtained; and more recently Lieutenant Berryman has found obsidian, pumice, etc., forming a line of volcanic cinders a thousand miles long, and stretching wholly across the Gulf Stream where the submarine cable is to be laid. Lieutenant Maury and others have found it difficult to determine the source of these volcanic materials. Occupying a line so extended, it is not unreasonable to suppose that submarine volcanoes were situated in or near the place where their products have been found. The specimens of animalcular life obtained from various seas place it beyond a doubt that the bed of the ocean is a vast cemetary consisting almost entirely of the remains of infusoria; and the unabraded appearance of these shells, and the almost total absence of any sand or other matter, seems to show that the bottom of the deep sea is in a state of perfect repose.

Although our author, in his chapters on the Atmosphere, and on Land and Sea Breezes, has treated generally of the Trade Winds, etc., and the Calm Belts which limit them, he devotes a long and valua