Sessional_Paper_1898 — Page 106

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The force of the wind is also different according to the dimension of the typhoon. On an average we have force 12 within 35 miles of the centre, force 11 at 50 miles, force 10 at 75 miles, force 9 at 110 miles, force 8 at 145 miles, force 7 at 180 miles, force 6 at 220 miles, and force 5 at 250 miles; but it often blows force 6 at 300 miles from the centre and then the area with strong wind is increased in proportion. Within from 2 to 15 miles of the centre the wind calms down, or nearly so, and the sky usually clears overhead, more or less, at sea (or over an island), being now covered there by only very light clouds or haze, through which the sun or the brighter stars are visible. The sea is often seen to boil like a cauldron. Its surface has been whipped into foam, and a lot of air has been caught by the waves, which

escapes under the low air pressure in the bull's eye of a typhoon. The sea is as a rule moun- tainous and confused, but sometimes near land it calms down when the diameter of the calm area exceeds 20 miles. Quantities of sea-birds, and, closer to the shore, also land-birds, butterflies, and other insects cover a ship caught in the centre of a typhoon. The centre of the calm area, round which the wind circulates, does not always exactly coincide with the point where pressure is lowest, , the centre of the isobars. It has been found that the calm followed some 20 miles after the lowest barometer reading, but such is not always the case, and the reverse has been suspected on more than one occasion. Very deceitful lulls occur during the raging of a typhoon. They last sometimes long enough to be mistaken for the central calm, but when the wind rises again it comes from nearly the same direction. Thus in case of typhoons moving W or NW in the China Sea in summer there is sometimes an area, some 60 or 70 miles behind or to the S of the centre, where the wind falls to a fresh or strong breeze, which again increases rapidly and even a couple of hundred miles farther

away it blows stronger than over that area. The diameter of the central calm in a low latitude in summer is about 4 miles, and the sea is mountainous from all directions, but farther north or late in the year the diameter reaches sometimes from 40 to 50 miles, and the sea then often goes down together with the wind, but the character of the bull's eye is then less well defined. The weather becomes dry, though in one or two cases torrential rain has been registered within the central calm. Inland in China the bull's eye has never been observed.

At the

When the wind rises in a typhoon it blows in gusts and the mercury heaves in the barometer. When the wind has reached force 11 it blows in fierce squalls of sometimes about 10 minutes' dura- tion, while the mercury heaves up and down as much as a tenth of an inch. The mercury often gives a jump upwards as the wind begins to veer in a squall. Then it drops down and gives another upward jump as the wind comes back to nearly its old direction. During these squalls an enormous quantity of rain falls in a few minutes. The temperature falls and rises a fraction of a degree or more. The wind does not return to quite the former direction, except just in front of the centre. time when the centre is nearest, a fierce squall is usually felt, and in that squall the direction of the wind changes considerably, and the barometer begins to rise. The squalls appear to be caused by an up-and-down movement of the air. As the air comes rushing down the rain drops evaporate in the hotter stratum near the earth's surface, and owing to the increased tension of water-vapour, the barometer (after a fall caused by the cold of evaporation) begins to rise. The wind veers towards the direction of the wind above, which latter is known from the motion of the clouds. Then the air starts to rise with a deluge of rain, caused by the condensation of vapour arriving at the cooler stratum above, while the barometer (after a rise caused by the heat of condensation) drops down, owing to the cessation of the pressure of water-vapour condensed into the rain fallen, and the wind resumes the direction determined by the central depression; for the latter is so great in a typhoon and gradients so steep near the centre that subsidiary depressions have never occurred in the China Sea.

It is a fact that more damage to vessels is caused by the fearful seas than by the wind. For- tunately masters of ships are now making use of oil to calm the waves, a remedy which has been used with good effect for the last three thousand years. Thick oil is best-mineral oil is of no use--- and it should be allowed to ooze out of canvas bags half full of cotton waste and slung from the weather bow, or it may be left to ooze out of other openings, such as water-closets.

It is still more effective when fired from the vessel towards approaching seas from mortars or rockets.

On shore perhaps as much damage is caused by rain as by wind; but, of course, the former adds impetus to the latter. The wind blowing from all sides into the centre raises the level of the sea there, and the sea-surface is also raised about a foot for every inch the barometer falls below its height outside of the typhoon. When this storm-wave approaches the shore near the time of high water, which somehow seems to happen rather often, it raises the sea, and is apt to cause extensive and disastrous inundations over low-lying shores, as the crests of the waves (which at sea may be 30 feet high or more) on entering shoal water may rise 60 fect or upwards above sea-level in a typhoon.

The incurvature of the wind in a typhoon depends upon the monsoon. In May, June, July, and August the angle between the wind (direction whence coming) and the bearing of the centre is 11 points in front of the centre, 10 points in the right-hand quadrant, 12 points behind the centre and 11 points in the left-hand quadrant. During September, October, and November it is 11 points in front, 11 to the right, 12 in rear, and 11 points to the left. This shows that the monsoon blows in

towards the centre and combines with the cyclonic winds. It will be remarked that the wind blows across the path in front and helps a vessel to run across the path in front of the centre, keeping the wind on the starboard quarter 3 points from the stern. In rear the wind blows more straight in towards the centre, and it also blows stronger in rear than in front.