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GOVERNMER NOTIFICATION.-No. 10.
The following report from the Director of the Observatory, is published for general information
By Command,
Colonial Secretary's Office, Hongkong, 7th January, 1888.
FREDERICK Stewart, Colonial Secretary.
RESULTS OF FURTHER INVESTIGATIONS CONCERNING TYPHOONS.
A pamphlet on The Law of Storms in the Eastern Seas, adapted for the use of the shipping ar embodying practically all that is now known about typhoons, was issued in September last year.
A distinguished German meteorologist in reviewing this pamphlet makes reference to the similarit which exists between the typhoons in the Far East and the hurricanes of the West Indies. An lifferences which may be ascertained must, I believe, be ascribed to dissimilarity between the coastline and islands, as the former. more especially, are found to have so great an influence on atmospheri isturbances.-The West India hurricanes may be divided into four classes. Those of the first class pas WNWestward to the south of Hayti and strike the coast of the mainland south of the norther promontory of Yucatan. Those of the second class pass generally NWestward and enter the Unite States. While those of the third class recurve generally between the West Indies and the Bermuda and pass away to the NE. Hurricanes of the fourth class, moving obliquely towards the equator in low latitude. are very rare.
My investigations on the typhoons in the past four years furnish already an insight into the sub-classes into which the different kinds of typhoons may be divided in the future. Thus the simi- larity between the paths of Typhoons V of 1885 and IV of 1886, Typhoons VI of 1885 and X of 1886, Typhoons XVII of 1884 and XVI of 1886, Typhoons X of 1885 and XVII of 1886 may be pointed out, the latter being particularly remarkable, so much so that doubts might reasonably have been entertained about its reality if the case had occurred but once.
Stormpaths in tropical seas are of a very simple nature,-much more so than in the case of minor depressions anywhere or storms in the temperate zones,-as long as the course lies far from any shore. That irregularities occur may be seen from such paths as are furnished by Typhoons VIII and XV of 1886. However there are while the typhoon is far from the shore seldom observations enough available to indicate small irregularities with certainty.
Whether a typhoon ever crosses the Pacific and Canada and reaches Europe is not known for certain. It is of course within the range of possibility, but must be doubted till clearly proved.
The coasts of China and Corea are now well furnished with stations. 120° 35′ E with observations made at 9 a, 3 p and 9 p daily was added on the 1st September, 1886, Wenchow in 28° 0′ N, and Chemulpo in 37° 29′ N, 126° 37′ E on the 1st November, 1886. Observations made hours were commenced on the 5th July, 1885, and were discontinued on the 27th February, 1887,
every three Port Hamilton in 34° 0′ N, 127° 20′ E.
in
The part of the Far East best supplied with meteorological stations is of course the Empire of Japan. One of the localities from which very poor information was hitherto available was the Philippine Archipelago, but the subject has now been taken up officially since a new Government Observatory was constructed. Meantime the want has been to some extent supplied by telegrams twice a day from Manila, by English volunteer-observers in Bolinao and Iloilo and by extracts from the logbooks of ships trading in the Archipelago.
Thunderstorms occur occasionally all round the centre of a typhoon in the ring of high pressure and gentle gradients beyond the area where the wind is fresh. Nearer the centre but before the wind Begins to rise the clouds generally assume the form of Roll-cumulus which prevails till full typhoon force is reached. The mean monthly height of the mercurial column is scarcely lowered in conse- quence of the typhoons as the high pressure all round the typhoon counter-effects the low pressure near the centre. The monthly mean solar radiation is lowered both with regard to intensity and to duration, while the true air-temperature, the tension of water-vapour and the rain-fall are increased. The mean force of the wind is increased very considerably in months when typhoons approach the neighbourhood.
When the wind rises in a typhoon it blows in gusts and the mercury heaves. in the barometer. In a strong gale the mercury fluctuates frequently three hundredths of an inch at intervals of perhaps about four minutes. But there is no heaving when the wind is not strong even if the centre is to a vessel. When the wind has attained storm-force it blows in fierce squalls of perhaps about ten very close minutes duration, while the mercury heaves up and down as much as eight hundredths of an inch. In these squalls the wind veers or backs in the direction towards which it is going to change owing to the progressive motion of the centre of the typhoon. As a general rule it may be said that the mer- cury gives a jump upwards when the wind begins to veer in the squall. Then it drops down and gives another jump upwards, while the winds shifts back to its original direction. But the mercury has been observed to behave in the opposite way greasionally and this point deserves furthon in main Page 1
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