Thomas Nelson

“ Now as the severity of a typhoon is measured by the velocity of the winds within the storm-disc—and we admit on the first principles that the greater the rapidity with which the currents revolve around the focus, the greater the condensation of vapour there, and hence the more perfect the vacuum at the centre—we shall have an explanation of the reasons why the barometer falls lower in a severe, than in a more moderate gale. ”

“ Nearly all writers agree that a typhoon is a circular storm-disc varying from one to ten miles in height, and in diameter from fifty to one thousand miles; and that the winds within the disc blow in circles—or nearly so—round a common centre, which is generally calm, and varying in size from one tenth to one fifth, and in some cases as much as one-fourth, of the whole diameter of the gale. ”

“ Colonel Reid may be said to have reduced the science to practical use by showing how safe rules for scudding, or lying-to in a hurricane, might be deduced from the theory, and how when obliged to lie-to, ships should do so on the proper tack according to the side of the path they are on; and lastly how these storms may be made profitable to ships bound in the direction of their track, by sailing carefully on the outer circumference with a fair wind, being all the time in a safe position to heave-to and let the storm pass. ”

“ At 3 a.m. 9th October, barometer 28.21, took in main top-sail, and put ship on starboard tack, being in the right hand semicircle; at 4.30 the scene was fearful; gust upon gust, and sea running high but not breaking owing to the wind. At 6 a.m. barometer 27.50, men lashed on deck, nothing visible of ship but a portion of her weather deck, on her beam-ends, yard-arms in the water. At 7 a.m. barometer 27.29, when suddenly it lulled and the centre passed. Drift, up to this time, 51/2 knots per hour, N.W., was expecting every moment to hear the ship crushing on the reefs. ”

“ Wherever such a mass should strike the Earth a hurricane might arise; and should two such masses meet in mid-air, a tornado of any degree of intensity on record might easily result from their combination.
Sir John Herschel further suggests that two great atmospheric undulations (which he terms barometric waves, because they are made evident by the fluctuations of the barometer) travelling in opposite directions and intersecting each other, from their opposing forces might cause the phenomena of hurricanes or rotary storms. ”

“ It seems worth inquiry, he says, whether hurricanes in tropical climates may not arise from portions of the upper currents prematurely diverted downwards before their relative velocity has been sufficiently reduced by friction on, and gradually mixing with, the lower strata; and so dashing upon the earth with that tremendous velocity, which gives them their destructive character, and of which hardly any rational account has yet been given.—Their course, generally speaking, is in opposition to the regular trade-wind, as it ought to be in conformity with this idea. ”

“ If this had been done at the beginning of the gale, she would not have approached the centre nearer than 150 miles; for the winds drawing to the Eastward, as the gale advanced to the Westward, she would have made no drift to the Southward, and she would have been in a safe position to receive the shifts—as each one would have been more aft—and the ship, coming up to the wind, would have been riding head on to the heaviest sea. ”

“ An extensive condensation of vapor going on in the centre, the air becomes lighter there than elsewhere in the revolving disc, and forms a kind of chimney for the denser air below to pass up through; and when this process has been going on for some time the air beneath is sufficiently exhausted to admit of the storm disc descending to the surface of the earth, after reaching which, it takes up a progressive motion and is impelled by magnetic attraction towards the magnetic poles. ”

“ He accounts for the production of clouds, the rise and fall of the Barometer by this cause, inferring, that at a certain height the rising air overflows the rest of the atmosphere, forming a ring of cloud vapor and air, which pressing on that below, occasions the rise of the barometer found at the edges of severe storms.
Mr. Thomas Hopkins of Manchester, in a work published in 1844, entitled “On the atmospheric changes which produce Rain, Wind and Storms,” admits with Mr. Espy the ascent and condensation of vapor in the air from various causes, and that all horizontal winds are thus produced. ”

“ The first indications by the barometer of the presence, in its vicinity, of a typhoon is generally its oscillations or restless condition, which, though sometimes very small, not exceeding 01 of an inch, ought never to be disregarded. ”

“ Draw another line through the centre, at right angles to the first, and it will be found at a point 90 degrees to the left of the first line or where the second line cuts the wind-circle. The direction of the wind will be parallel to the first line; hence, standing at this point and looking in the direction of the wind’s eye, and parallel to the first line the centre will be 90 degrees to the right, or on the right hand.
As a practical example I will take the typhoon which passed over Yokohama on August 25th, 1872, and which this diagram is intended to represent. ”

“ This diagram shows the centre to have passed over this place, and this is made evident (in accordance with the law) by the wind remaining nearly stationary during the first half of the gale, a thing which can only occur when the centre is travelling directly towards you, or when running on a course parallel to the course of the “Typhoon”—keeping the bearing of the centre the same as with the bearing of the centre, the wind must always change. ”

“ But we also find the barometer standing lowest at or near the centre, and this may be accounted for by the fact of a partial vacuum existing there from condensation of vapor, and the surrounding air rushing in to supply the vacancy, leaves room for neighbouring currents to expand and become lighter, a process which on this principle I suppose to be going on from the centre towards every part of the outer circumference ”

“ It turns or blows round a focus or centre in a more or less circular form, and at the same time has a straight or curved motion forward, so that, like a great whirlwind, it is both turning round and, as it were, rolling forward at the same time. ”

“ Birds—Kites and Vultures—are often seen soaring high up, just above these spouts, apparently following the direction of the column, as if enjoying it.
My idea is that the phenomena connected with dust-storms are identical with those present in waterspouts and white squalls at sea and revolving storms and tornadoes of all kinds; and that they originate from the same cause viz—moving columns of electricity. ”

“ He considers also that the ascending winds produce descending ones, and that the rain produced in the higher regions brings air and vapor with it in its descent, and thus constitutes the lower atmospheric currents ”

“ Mr. Peddington relates the case of the “Earl of Hardwicke”, Captain Neller, as follows:—
“In the Southern Indian Ocean, when near the borders of a typhoon, she was standing off and on to keep out of it; and describes the weather as being squally, thick, heavy and wild looking; the upper clouds coming from N.W.; the next stratum N.E.; and the lower scud, with the wind, fast from S.E. The trades (S.E.) were blowing strong—but at midnight ran into a dead calm; the breeze soon sprung up again, and the next day had a high, confused sea, barometer rising from 29.95 to 30.00. ”

“ This would not have occurred a second time, as an equilibrium of forces was soon established, and the pressure equalized on both sides.
There are two essential rules of vast importance to the seaman to be remembered in connection with circular gales, and which will always be a sure guide. ”