sult is somewhat remarkable; and, though the number of my experiments may not entitle me to deduce from them a general law, yet their publication may excite the attention of those who have opportunities of repeating them. The specimens of sea-water were procured at my request by nautical friends some time ago; but all were taken up within the same year. Each specimen filled a common glass bottle, and had a label immediately affixed to it, indicating the place where it was obtained. The water, from considerable depths, for want of better apparatus, was procured by the following contrivance. It was found that a bottle might be so corked as to prevent the admission of water, until the pressure of the superincumbent column, on sinking it by an attached weight, pushed the cork inwards, when the escape of the air, and the filling of the bottle with water, again forced the cork into its neck, and thus obviated the change of displacement of the included water, as the bottle was drawn upward. The pressure required to force the cork being ascertained by previous experiment, the bottle, thus prepared, was sunk to the requisite depth; and, after remaining there for half an hour or more, was drawn up and immediately secured.

My experiments were carefully conducted by means of a delicate balance, and a thin flask, capable of holding upwards of 1050 grains of distilled water, when its ground stopper was adjusted. A bottle of distilled water, and all the specimens of sea-water, were reduced to the same temperature, by being placed for many days on the same table, in a room without a fire: and, to prevent error from this source, each liquid was examined by a good thermometer previously to the experiment. The weight of the distilled water bearing the same ratio to the weight of an equal volume of the other fluids, as 1.0000 to the sought specific gravities, is the simple formula from which the following table is deduced :— Table of Specific Gravities at Temperature 51°

ditto

Fahrenheit.

= 1.0286

1. Sea-water drawn from the surface, lat. 47° 47' N., long. 10° 40′ W. 10277 2. Ditto from the depth of forty fathoms, ditto, 10280 3. Ditto from the surface, lat. 37° N., long. 9° W. off Cape St. Vincent 10281 4. Ditto from the surface, Maderia, bearing north-east distance, sixteen leag es 1.0284 5. Ditto from the depth of forty fatnoms in the same spot 6. Ditto from the depth of thirty-six fathoms, lat. 26° N., long. 64° W., during a voyage to Demerara 10287 7. Ditto from the surface, lat. 92° 11' N., longitude not given; but, as it was in the same voyage as No. 6, it was probably more to the west 10289 8. Ditto from the surface, lat. 8° 20′ N., longitude not given; but as the three last numbers were obtained in the same voyage to Demerara, and this one, at my request, was taken when the captain supposed that he would make land in a day or two, there can be little doubt of the ship being at this time just off the mouth of the Orinoco 10267

In calculating these specific gravities, I had carried them to several decimal places farther; but I have suppressed these in the Table, because it might appear an affectation of accuracy which the case does not admit; for the difference of a single one-tenth of a grain in weighing each fluid in the above experiments, would make a difference of nearly th in their specific gravities; or would alter the last figure of the present decimal series.

The inferences to which these experiments lead are, 1st. That the specific gravity of the waters of the Atlantic increases as we approach the equator. 2d. That the specific gravity of seawater increases with the depth from which it is drawn.

The only exception in the table to the first inference is No. 8; but the great diminution of density here observed is undoubtedly owing to the vast mass of rushing water poured into the ocean by the Orinoco, the stream of which is said to discolor the sea many leagues from land, and at a considerable distance from the shore to preserve the freshness of its current.

The results of captain Scoresby's experiments, on the specific gravity of sea-water, seem to agree with the inferences above mentioned. This intelligent navigator found that the density of the waters of the ocean, near the meridian of Greenwich, gradually diminished from lat. 57° 42′ N., to lat. 66° 45'; being at the former 10280, at the latter 10263. In higher latitudes, or in confined seas, we cannot expect to find a uniformity in such results; for the influence of the ice in the one, and of situation in the other, are sufficient to conceal such minute differences. On referring to his valuable work, an examination of his experiments on the density of sea-water, at different depths, will confirm also the second inference. The few exceptions to it in captain Scoresby's Table may be explained by the influence of currents, and irregularities produced by the neighbourhood of ice, which is known to exercise a powerful influence on the atmosphere, and on the waters. In the prosecution of this interesting subject, no instrument appears more admirably adapted to procure water from any required depth, without chance of error, than that gentleman's marine diver; which, with simplicity of construction, unites every property that can insure accuracy and convenience in those delicate investigations for which it was intended by its ingenious contriver.

'I am at a loss, adds this writer, what reason to assign for the increased density of water brought up from considerable depths; unless, according to a suggestion offered by my friend Dr. Brewster, it may be owing to the imperfect elasticity of water, which prevents its particles, when compressed by the superincumbent column, from regaining their original condition, when the pressure is removed. A curious series of experiments might be made on the mechanical compression of water, by employing the bathometer of Mr. Perkins, the inventor of the method of multiplying copper-plates by engravings on steel. In this machine, water enclosed in a brass tube, the sides of which need not exceed one-tenth of an inch in thickness, is com

pressed by a solid piston, sliding in a leather collar, and acted on by the superincumbent column when sunk in the depths of the ocean. This seems one of the simplest means of producing an immense pressure; and, when conversing with Mr. Perkins, I remember his stating that the piston did not exactly return to its original position, on bringing up the instrument.'

Dr. Horner has embodied the result of his observations in a table which demonstrates the facts also proved by the experiments of Krusenstern's voyage, that the sea on the surface, between the tropics, is specifically heavier, and that it contains more salt, than in higher latitudes. If we take together the statements from 25° S. as far as 25° N. lat., and in the same manner, from 50° to 65° of N. lat., the mean of the first is 1.0288, that of the latter 1-0245, which gives the difference of 0.0043 or But this by no means proves an absolute inequality in the saltness of the water in general. To give a decided opinion on it, the sea-water must be fetched up from considerable depths, and weighed. Probably the greater saltness arises from the rapid decrease of the fresh water, in consequence of evaporation. From the well known slowness of the transition of chemical elements, in undisturbed compounds, this decrease is but slowly repaired; and, as the upper layers are also the warmer, they may, notwithstanding their greater specific density, in consequence of their extent, be maintained by the warm swimming above the lower cooler layers, by which a principal agent of commixture, the difference of weight, is rendered of no effect. The slowness of change, and the condensation of the saline solution at the surface, which results from it, has the advantage that the acceleration of the evaporation sets bounds to itself, because, with the increasing condensation, the attraction of the salt to the parts of the water is greater, and, consequently, the diminution of the latter less. Without this arrangement the tropical seas would perhaps be covered, like the frozen seas of the north, with constant fogs. Subsequent experiments will show how far our explanation of this inequality is correct; of which we have now more hopes, as convenient accurate apparatus have been discovered to fetch up water from any depth, at pleasure, and unmixed.

The considerable number of observations (there are 116 of them) on the temperature of the sea below the surface, their extent over waters of the ocean remote from each other, and probably, also, their accuracy, give them a decided claim to the attention of the natural philosopher; and the perseverance with which they were continued, under various circumstances, does honor, as well to the naturalist of the expedition, as to the commander, who not only in calms, but in some periods almost daily, afforded the necessary assistance. They were all made with Six's Thermometer, which is a good assurance of their accuracy. It is certainly remarkable that an instrument so simple, so convenient in the use, so certain in the results, and which has been long known, is not more frequently used for this purpose; so that in the latest scientific voyages much more uncertain thermometers

have been used, to which only the deep sea clamın of captain Ross forms an exception. Our observations fall under two heads: measurements of the temperature in different depths, in the same places of the ocean, and in statements of the warmth in the usual soundings, from sixty to eighty fathoms, in different places.

The most complete observations on the changes of the temperature, in increasing depths, are, in the South Sea, of the 13th and 14th of September, 1817, in 36° N. lat., and 148° W. long. Besides confirming the general law, that the cold increases with the depth, they also afford the following results:-1. The upper parts of the water show a particular warmth, as the temperature, in the first eight fathoms, diminished only 0°4', R., but from that depth to twenty-five fathoms full 6°, R. From twenty-five to 100 fathoms' depth the decrease of warmth is considerably less, since in the next twenty-five fathoms, it is only 1° 7′, R., and in the next fifty fathoms only 1° 5, R.; a decrease which amounts to only the tenth part of the preceding. It is still slower between 100 and 300 fathoms. 2. If we compare these observations with those of the 6th of June 1816, in 37° N. and in 199° W. long., consequently in the same parallel of latitude, the influence of the season is particularly observable in the temperature on the surface, which in June is 13°, R., in September 18° R. It, however, does not go much deeper than from twenty-five to fifty fathoms; and at 100 fathoms it is already within the limits of the accuracy of such observations; for we have

For 100 fathoms

6th June 9° 4' Reaum. 13th September 9 4 14th September 8 6 3. A certain coincidence with these results, only on a greater scale, is shown by the experi-. ments of the 15th of November, 1817, in 9° N. lat., and 205° W. long., in which the temperature decreases from the surface to about sixty or seventy fathoms, rapidly and uniformly, from 24° 7′, R., to 8° 8', R. From nine to 101 fathoms, this rapid decrease, instead of proceeding, is suddenly reduced to the small amount of 0° 9', R. But if we compare these observations with those immediately preceding and succeeding them of the 13th, 14th, and 17th, of November, we shall hesitate to draw from them decisive conclusions.

4. The observations of the 13th of April, 1816, in 15° S., and 130° W., follow a quite different course from those in September, 1817, in 36° N. The decrease of warmth from the surface, to as far as 100 fathoms' depth, is much more inconsiderable, being here only 3o 6', there nearly treble, namely, 9o 4', R. It becomes more considerable between 100 and 200 fathoms, namely, 8° 8', R. Remarkable as this inequality is, it yet seems impossible to ascribe it to an error in the observation, such as too soon drawing up the thermometer: for, on the one hand, the regular course of the experiments of the 14th of September, 1817, and their coincidence with those of the 13th, at the depths of 0° 25′ and 100 fathoms, does not allow us to suppose any thing of the kind; on the other side, the observations of the 13th of April, 1818, find their

Id.

Id.

the

Bacon.

The sense is like the sun; for the sun seals up lobe of heaven, and opens the globe of earth; so the sense doth obscure heavenly things, and reveals earthly things. They their fill of love Took largely, of their mutual guilt the seal. Milton. Back to the' infernal pit I drag thee chained, And seal thee so as henceforth not to scorn The facil gates of hell, too slightly barred. The prominent orifice was closed with sealingwar. If the organs of perception, like wax overhardened

Id.

Boule.

with cold, will not receive the impression of the seal; or, like wax of temper too soft, will not hold it; or else supposing the wax of a temper fit, but the sel not applied with a sufficient force to make a clear impression in any of these cases the print left by the seal will be obscure.

Locke.

He saw his monkey picking the seal wax from a Arbuthnot.

letter.

The same his grandsire wore about his neck In three seal rings; which after, melted down, Formed a vast buckle for his widow's gown. Pope.

A SEAL is a stamp of metal, stone, or some other convenient substance, whereon are engraven the arms, device, &c., of some prince, state, community, magistrate, or private person, often with a legend or inscription; the impression whereof in wax serves to make acts, instruments, &c., authentic. The use of seals, as a mark of authenticity to letters and other instruments in writing, is extremely ancient. We read of it among the Jews and Persians in the earliest and most sacred records of history. And in the book of Jeremiah there is a very remarkable instance, not only of an attestation by seal, but also of the other usual formalities attending a Jewish purchase. In the civil law also seals were the evidence of truth, and were required, on the part of the witnesses, at least at the attestation of every testament. But in the times of the Anglo-Saxons they were not much in use in England. For though Sir Edward Coke relies on an instance of king Edwyn's making use of a seal, about 100 years before the conquest, yet it does not follow that this was the usage among the whole nation, as we are assured by all our ancient historians that sealing was not then in common use. The method of the Saxons was for such as could write to subscribe their names, and, whether they could write or not, to affix the sign of the cross; which custom our illiterate vulgar to this day keep up, by signing a cross for their mark when unable to write their names. This inability to write his name, and therefore making a cross in its stead, is honestly avowed by Cadwalla, a Saxon king, at the end of one of his charters. For the same unsurmountable reason, the Normans, a brave but illiterate nation, at their first settlement in France, used the practice of sealing only, without writing their names; which custom continued when learning had made its way among them, though the reason had ceased; and hence the charter of Edward

the Confessor to Westminster Abbey, himself being brought up in Normandy, was witnessed only by his seal, and is generally thought to be the oldest sealed charter of any authenticity in England. At the Conquest the Norman lords brought over into this kingdom their own customs; and introduced waxen seals only, instead of the English method of writing their names, and signing with the sign of the cross. The impressions of the seals were sometimes a knight on horseback, sometimes other devices; but coats of arms were not introduced into seals till about the reign of Richard I.

SEAL is also used for the wax or lead, and the impression thereon, affixed to the thing sealed. The color of impressions of seals has varied considerably. That sort of wax most anciently used was white. The employment of yellow wax on public documents prevailed a good deal about the twelfth century. Ultimately, however, red wax became preferred in almost all the European countries, and remains so at the present moment. The western patriarchs and emperors sealed in green wax certain letters to persons of distinction. This usage was adopted in the twelfth century in France, and at a date somewhat subsequent introduced into Germany. Specimens of this variety are however extremely rare. In our own country the green seal is still occasionally used on charters. The emperor Charles V., in 1524, accorded the privilege of sealing in blue, but the example is unique of the employment of that color among European potentates. Certain princes have, at different times, adopted black wax to seal withal; as, for instance, Jeremy, patriarch of Constantinople. In the thirteenth century it was employed in France. Impressions are also found in mixed wax, i. e. of different colors. Seals vary, besides, in size and shape; they are sometimes large, sometimes small, square, round, long, trefoil, lozenge, &c.

SEAL, in zoology. See PHOсA.

SEAL, KING'S GREAT, is that whereby all patents, commissions, warrants, &c., coming down from the king, are sealed; the keeping whereof is in the hands of the lord chancellor.

SEALER is an officer in chancery appointed by the lord chancellor, or keeper of the great seal, to seal the writs and instruments there made in his presence.

SEALING WAX. See WAX SEA-LION. See PHOCA. SEAM, n. s. & v. a. SEAM'STRESS, SEAMY, adj. the two edges of cicatrice; scar: a ployed in sewing

seams.

Saxon ream; Goth. seym; Belg. zoom; Teut Ssaum. The suture where cloth are sewed together; a seamstress is a woman emseamy, having or showing