be consulted for warnings, particularly at night, when its falling is very remarkable. It is well known that it generally rises with westerly winds changing to North and East, and falls with the winds from the opposite quarters. But instances of the contrary are known, which are not surprising in so confined a sea as that of which we are treating, in which opposite winds are blowing at the same time.

When the barometer falls to 29.45 inches, bad weather must be expected, especially if large massive clouds are collected, or dark gloomy weather comes on, with ash coloured clouds; while, when it rises to 30-35 inches, it is a promise of fine weather. Its mean height ordinarily is 30-00 inches.

Most frequently a great fall in the barometer indicates only that there will be a heavy fall of rain. The mercury will be seen to fall as the sky clouds over, inducing the navigator to take all kinds of precaution against a severe gale; and instead of blowing, heavy showers come down without the least breath of wind; and the mercury rises again in proportion as the sky becomes clear. It is true that occasionally clouds which presented the appearance of rain are resolved into wind. For this reason, without placing an implicit reliance on the movements of the barometer, it should be consulted, to obtain an idea at least of the winds which may probably prevail.

In the gulf of Lyons the barometer is nearly always high with winds from East to S.E.; but low with the same winds when they are rainy. It is also high when light westerly winds prevail. The maximum height which it reaches at Toulon is 30-50 inches, and this is generally in February with S.E. winds, attended with fine weather and a low condition in the height of the sea. There was a year when the barometer rose to 30-70 inches, remaining stationary for many days, with an extraordinary low state of the sea in the harbour. This low condition of the sea is experienced every year in January and February at the port of Mahon. The natives call them secas de Janer, and it generally continues fifteen or more days, in the midst of fine weather.

In Algiers the mean maximum height of the barometer for a period of six years' observations was 29-58 inches, occurring in December with winds from S.W. to N.W. The maximum height was 30-40 inches, occurring in February with N.E. and easterly winds, and coinciding with the same observations at Toulon. The mean height generally is 29.95 inches. The highest state of the barometer ever known was with easterly winds, and the lowest with westerly.

In the gulf of Valencia it is generally high with easterly winds and a clear sky; and low with the same winds when increased to a gale. The highest state of it observed at Valencia was 29.75 inches in April, with easterly winds, fine; the lowest was 29-28 inches in October, wind N.E., foul weather.

In the Strait of Gibraltar the highest observed was 30-45 inches, in December, January, and February, with N. W. winds; and the lowest 29.90 inches in April, with winds from the S. W. quarter.

Thunderstorms.-The barometer usually falls when the atmosphere is charged with electricity, and in this case its falling is the forerunner of thunderstorms. These mostly occur at the changes of the seasons, when the strong opposite winds and rains take place. They are common in the Strait of Gibraltar, off Cape San Antonio, and in the vicinity of the gulf of Valencia and that of Lyons. According to some statements of Admiral W. H. Smyth, in his work on the Mediterranean, the severest and most numerous disasters produced by lightning on board ship have occurred in September, October, and March; and two thirds of these at night, between midnight and sunrise; mostly falling on the main mast. They occur in summer in the gulfs and bays both of Spain and Africa when the sea breeze encounters the land winds; by these contacts forming waterspouts, which in some parts are tolerably frequent, especially in August and September. These waterspouts usually go off in rain and heavy electrical discharges; but they also produce severe squalls, on which account ships should be prepared for them with reduced canvas.

In these conditions of weather waterspouts are not uncommon, and although they commonly occur at any time of the year, they are more so at the change of seasons, especially in the autumn. They are generally formed when clouds meet together, brought by opposite winds, and are more frequent off projecting capes and places where these opposing winds meet; and thus they are common in the Strait of Gibraltar, off Cape de Gat and San Antonio, off Cape Creux and the Balearic Islands, and are tolerably frequent on the coast of Africa. Occasionally several are seen at once, and a vessel has been becalmed with no less than seven around her at once, all seen moving in different directions.

The

They will form sometimes part of the heavy storms of rain which are driven against the prevailing wind. The brig Invincible, while cruizing on the coast of Spain, on her way between Cadiz and Algeciras, in the end of December, 1834, met an easterly wind in the Strait of Gibraltar, blowing hard, while in the Atlantic the S.W. wind was blowing, with rain, evidently passing over the former. brig reached the narrow part of the strait with close reefed topsails over reefed courses and foretopmast staysail. With each storm of driving rain from the S. W. which passed over the vessel from to leeward to windward the force of the easterly wind increased to that degree that she was obliged to take in the courses, and a waterspout was formed at the same moment to windward, appearing as if it came from the side of the vessel, moving rapidly to the eastward. In proportion as the waterspout moved from her the wind slackened, and allowed the vessel to set her courses again. A quarter of an hour had scarcely passed when another rain squall came on her, producing the same phenomenon of forming a waterspout on the weather side of the vessel, which was observed as it passed away from her as before. As the squall passed over, a large amount of heavy rain was discharged, and so violent was the wind that it was necessary to take in the

courses again and run for shelter under Cape Espartel. The strength and violence of the levanter (the easterly wind) kept on blowing against the hard S. W. wind for twenty-four hours; and no squall came up from the S.W. into the strait that did not produce a waterspout, until the levanter suddenly ceasing left a free passage for the vendaval (S. W. wind) and its heavy clouds, but without the formation of any more waterspouts.

When the vessel, on the previous day, was off Cape Trafalgar, the wind was not steady, notwithstanding the contest between the two winds. But off Cape Spartel several of these meteors were seen, hanging from compact masses of cloud of the nimbus order, the rain cloud.

If there is a steady wind it is easy to avoid a waterspout, because it occupies but little space as it moves on its course. But if a vessel remain becalmed, and the meteor appears to be coming upon her, nothing remains for her but to clue up every sail and secure the yards. If she has any artillery on board she might try, as some have advised, to break it by their discharge, or with some to pierce it, a mode of disposing of it practised with success sometimes.

It is not probable that a waterspout would produce the mischief that it is generally considered it would in a large vessel, nor that it would cause her to founder, unless she received its whole mass unprepared and with all sail set. It is more probable that it would carry away her sails. Small craft should indeed avoid contact with them; and when they do not care to do so should receive them with as little sail set as possible and present the stern to them.

Sometimes they will form rapidly and are suspended from a cloud over a vessel; in which case she should manœuvre quickly to avoid them, taking in all sail. When a case of this kind happens at night the meteor is not perceived, and the first notice the ship has is generally the loss of her sails from the whirling force of the wind. an experienced eye knows well the clouds that will produce waterspouts, and does not lose sight of them when they are likely to be forming.

But

Most frequently when these phenomena occur it is in calm or very light variable winds; and consequently, at night, the noise which they make on the surface of the sea is distinctly heard as they move onward, and apprises the navigator of their proximity and the direction they are taking.

The clouds which produce this singular meteor are generally nimbus and cumulostratus, which are generally well defined at their base (called by the Spaniards cejas): and from this the syphon proceeds, which continues extending downwards until it reaches the water. And as generally beneath it there is a clear, the meteor is very distinct, and its whole form may be traced from its origin to its dissolution. Sometimes it appears to conceal itself within the cloud, to return apparently after a little time in more extended proportions.

Of the producing causes of this meteor we are still ignorant, al

though there are some who ascribe them to electrical currents, combined with aerial. It is probable, or at least the effects on the surface of the sea seem to render it probable, that a waterspout appears to have its origin in a cloud on which different winds are blowing, and that on leaving the cloud it descends vertically to the surface of the sea, and by its falling brings with it a portion of the cloud, the ends or outer parts of which disappear until acquiring the form of an inverted cone; that if the waterspout does not bring with it watery particles, its effect is only seen on the surface of the sea by the water of it being forced upwards from round the furrow which is formed where it entered vertically, and that the phenomenon lasts until the cloud is exhausted of the whirling aerial matter which it contained. The waterspout progresses onward with the cloud which produced it as it glides along, and vanishes as soon as this becomes dispersed. If we imagine all the wind which accompanies a cloud to be combined in a waterspout, an idea may be formed of what it is.

Sometimes whirlwinds, composed of wind only, in the midst of a calm and clear sky, are observed moving over the surface of the sea, and would pass invisibly to the navigator if their progress were not indicated by the water which they disturb and the noise proceeding from them, this being heard when they are near. But these whirlwinds, never so violent as the waterspouts are, still resemble them in their effects, the only difference being that they are invisible.

It is considered by some that waterspouts draw up water from the sea when they descend down to it, founding their supposition on the effervescing water observed round it on the surface of the sea. The agitation which the water acquires is the effect of displacement occasioned by the force of the whirlwind falling vertically on the water, and producing a circular dell tolerably deep and sometimes from forty to fifty feet in diameter, according to observation. This dell may be compared with that produced on a small scale in the water of a basin, when it is blown down through a tube held vertically from the mouth. Waterspouts have not always the same violent motion, and it is probable that their strength bears proportion to the degree of wind which the cloud contains. A waterspout may pass at a very short distance from a vessel without harming her; and instances might be quoted as having occurred at sea and in port of their passing only twenty fathoms from vessels under sail or moored in harbour without doing them the slightest damage.

The presence of waterspouts indicates always great opposing currents in the atmosphere, some taking one direction and some another, according to the direction of the wind acting on the cloud which produces them, and with as much swiftness in that as in this. The clouds which produce these meteors are generally at low altitudes and of great density.

(To be continued.)

THE SEA COASTS BETWEEN ANTWERP AND BOULOGNE.-The Causes which have Changed the State of the Coast of the Scheldt to Calais.

(Continued from page 230.)

In the time of Julius Cæsar the interior country near these coasts was full of marshes, a condition which accounts for the presence of turf in a great portion of it. It appears also that these marshes were covered with a bed of clay, which has transformed them into fields of astonishing fertility. Lastly, that the soil of this part of the country is scarcely level with the sea; that the bed of clay is seven or eight feet thick; and that the turf is nearly the same thickness below it;-making the marshes the depth of fifteen feet below the level of the sea.

Where, then, is the cause of all this remarkable change? Let us first consider the possibility of fresh water marshes existing so near the sea and at fifteen or twenty feet below the surface, and how it happens that after a long succession of centuries the sea has penetrated this part. It is proved by the reeds found in the lower portion of this turf that the former marshes were caused by fresh water. We know that turf is generally formed in marshy ground and, although some have advanced the contrary, that it is not formed with marine plants Turf has been formed in a low pasture, although it might have been dry from the month of March; and this turf was recent, because the bottom of the pasture belonged to the bed of clay previously mentioned. It is constantly formed on barren heaths and in places which are never under water.

Marshes having existed below the level of the sea, it follows that during the number of centuries necessary for the formation of turf, there must have been between these marshes and the sea some obstacle to prevent the invasion of the latter. This may be thus accounted for :-The basin in which these marshes are found, and which, as we have seen, forms a plain composed of a bed of fine sand, while below this turfy and marshy stratum bears numerous proofs of the former presence of the sea. During its presence the N.W. border will have formed a succession of banks similar to those now off the coast. Some event, the cause of which is unknown, must have lowered the level of the sea or raised the level of the bank several feet, accounting for these banks being dry. These banks being once dry, downs would soon form, raising them still higher, and opposing a new barrier to the progress of the sea. This having no access into the basin, the sea water which was there would evaporate, and be in a measure replaced by rain water; which, uniting in the lower part with the other, would form those marshes spcken of by Cæsar, which have produced the bed of turf.

But the sea, which has only a slight effect on anything entirely submerged in comparison with that on the surface, will not have found in these new limits an obstacle opposed to its violence which it