72
Last of all we have the barometer as a measurer of the distance from the centre, and although but little reliance ought to be placed on this, yet in some cases it might be of use in determining what to do with a ship caught in a typhoon.
By comparison of a great number of cases Mr. Peddington has constructed the following table, intended to guide the mariner in estimating the distance from the centre.
| Average fall of Barometer. | Distance from centre. | ||||||
| (Per hour.) | In miles. | Intime | |||||
| From. | To. | From. | To. | ||||
| 0.02 | 0.06 | 250 | 150 | 12 | hours. | ||
| 0.06 | 0.08 | 150 | 100 | 9 | hours.„ | ||
| 0.08 | 0.12 | 100 | 80 | 6 | hours.„ | ||
| 0.12 | 0.15 | 80 | 50 | 3 | hours.„ | ||
The above table gives the average of a great number of barometer readings observed during typhoons principally at shore stations, where the observations have been made accurately and regularly, and from which the distance corresponding to each reading has subsequently been ascertained; but nothing is shown here nearer than three hours before and after the passage of the centre; the averages here registered apply respectively to 12-9-6 and 3 hours from the centre as marked in the table. After a typhoon has been blowing nine hours, no average fall can well be stated, as sometimes the barometer continues to fall at the same rate, and at other times (in cyclones of what Mr. Peddington calls the first class) falls when nearer than three hours from the centre, at a rate in proportion as 1 to 4 when compared with that of the former three hours.
It we examined the barometer readings during the typhoon which passed over Yokohama in August 1872, we shall find that this rule nearly corresponds with what was observed by myself during that gale.
It will be remembered that the diameter of this typhoon was 105 miles; its semi-diameter 5212 miles; that the entire storm-disc was seven hours passing over the
