Hours from midnight
to midnight.		Mean pressure
of atmosphere.		Direction of wind.Strength of wind 0 to 10.
17th August.
129.908S.E. 3⁄4 E.3.5
2.912 S.E. by E. 1⁄4 E.3.5
3.915 S.E. by E. 1⁄4 E.3.5
4.917 S.E. by E. 1⁄2 E.2.5
5.914 S.E. by E. 1⁄4 E.2.5
6.913 E.S.E.2.5
7.909 S.E. by E. 3⁄4 E.2.5
8.899 E.S.E.3.
9.886 S.E. by E. 1⁄2 E.3.
10.878 E. by S. 1⁄4 S.3.
11.869 E. 3⁄4 S.3.
12M..860 E. 1⁄4 S.3.
1.852 E. 1⁄2 S.3.5
2.853 E. 1⁄2 S.3.5
3.848 E.3.2
4.834 E. 1⁄2 N.4.
5.817 E.N.E.4.
629.808 E.N.E.4.
7.810 N.E. by E. 1⁄4 E.4.
8.812 N.E. by E. 1⁄4 E.3.5
9.812 N.E. by E.3.5
10.806 N.E. by E. 1⁄2 E.3.5
11.795 E.N.E.3.5
12.784 E.N.E.3.5
18th August.
129.779 E. by N.3.5
2.771 E. by N.3.2
3.762 E. by N.3.2
4.758 E. by N.3.2
5.751 E. by N.3.5
6.740 N.E. by E. 1⁄2 E.3.5
7.721 N.E. by E.4.
8.696 N.E. by E.4.5
929.666 N.E. by E.5.
10.640 N.E.5.2
11.612 N.E. 1⁄2 N.5.7
12M..581 N.E. by N.6.5
1.548 N.E. by N. 1⁄2 N.5.
2.526 N.E. by N.6.5
3.50 N.7.5
4.482 N. by E.7.
5.459 N.E. by N.7.5
6.435 N.E. by N.8.
7.421 N.E. by N.8.
8.411 N.E. by N.8.
9.408 N.E. by N.8.
10.405 N.E. 3⁄4 N.8.5
11.401 N.E. 1⁄2 N.8.7
12.375 N.E. 1⁄2 N.8.7
19th August.
129.306 N.E. by N.5.7
2.319 N. by E.8.
3.335 N. by E.7.
4.351 N.7.5
5.364 N. 1⁄2 E.7.2
6.376 N.7.2
7.383 N. by W.6.5
8.376 N. by W. 1⁄2 W.7.2
9.361 N.N.W.7.7
10.347 N.N.W.8.
1129.324 N.W.8.
12M..295 N.W.8.
1.268 N.W. 1⁄2 W.7.7
2.252 N.W. by W.7.5
3.238 N.W. by W.7.7
4.223 N.W. by W. 1⁄2 W.7.7
5.220 W. by N. 1⁄2 N.8.
6.221 W. by N. 1⁄2 N.8.
7.225 W. by N. 1⁄2 N.8.
8.229 W. by N.8.5
9.233 W.8.5
10.243 W.8.5
11.256 W.8.5
12.282 W. by S.9.
20th August to noon.
129.351 W. by S. 1⁄2 S.9.
2.363 W. by S.9.
3.375 W. by S.9.
4.413 W. by S.9.
5.437 W.S.W.7.5
6.457 S.W. by W.7.
7.457 S.W. 1⁄2 W.6.
8.471 S.W.6.
9.489 S.W. 1⁄2 S.6.5
10.505 S.W. 1⁄2 S.6.5
11.512 S.W. 1⁄2 S.6.5
12M..515 S.W. 1⁄2 S.6.5

The barometric readings are corrected to the freezing-point density of the atmosphere, as also to the level of the ocean, and are further reduced by comparison with the Standard Barometer at the New Observatory.

They are also relieved of a source of error arising from the regular decline for each day of the barometer, as evidenced by the observations made during June and July, 1858, in mean latitude 23° 52′ N., mean longitude 119° 12′ E. This downward tendency will be apparent from the following readings for each hour:—for 1h. (A.M.) - 0.004, 2h. - 0.005, 3h. - 0.0012, 4h. - 0.015, 5h. - 0.012, 6h. - 0.006, 7h. - 0.02, 8h. - 0.012, 9h. - 0.021, 10h. - 0.02, 11h. - 0.018, noon - 0.015, 1h. - 0.008, 2h. - 0.007, 3h. - 0.021, 4h. - 0.025, 5h. - 0.023, 6h. - 0.015, 7h. - 0.008, 8h. - 0.001, 9h. - 0.008, 10h. - 0.014, 11h. - 0.015, 12h. (midnight) - 0.011. These quantities are to be read as implying that when added to or deducted from those supplied by actual observations, they result in the quantities already assigned as the corrected averages for the day. The direction as well as strength of the wind are copied from the averages as calculated by the Commodore from the ship's log, the meteorological journals and the daily postings made by the Commodore himself.

According to the delineation of the path of the cyclone, as prepared from the observations recorded, the following table, already referred to, gives the approximative distance of the ship at stated points from such central path, as compared with that deduced from barometrical observations, allowing for the differences already mentioned. In the case of the wind-pressure, the average is deduced from the mean of successive observations taken every hour, and for the most part divided into intervals of three hours each.

Distance.Air-pressure.Difference.Distance according
to curve.
117thAugust4 A.M.33629.915 in. 336
2""noon.297.8600.055300
318th"midnight.265.783.132257
4""6 A.M.230.736.178233
5""9 A.M.205.667.248205
6""6 P.M.153.438.477153
719th"3 A.M.140.335.580138
8""5 A.M.148.364.551142
9""8 A.M.146.373.542143
10""noon.125.296.619130
11""3 P.M.123.238.677122
12""6 P.M.134.222.693138
13""9 P.M.148.235.680144
1420th"midnight.183.296.619183
15""6 A.M.313.450.465313

The minimum pressure according to the curve would be 28.975, but must actually have been less. According to the strict reading it would result that all radii before reaching the point where nearest the central path, as also all those in the same half-circle after such central line has been crossed, should have the same value, whatever the direction, which if rigidly asserted cannot be correct, since the motion of a cyclone is truly circular only in the immediate vicinity of its central point. As that point is receded from, the motion becomes more or less elliptical, as is attested by the barometric differences, which had the cyclone been a true circle in all its parts ought to be similar for similar distances. This it is admitted is not the case, as the barometric pressure shows a marked decline in the earlier part of a cyclone the more rapidly the central line is approached, just as it rises again once that line has been passed.

For this reason the distances as assigned upon a line of curves deduced from the foregoing observations must be too great, especially those which are calculated at right angles to the path of the typhoon, because perpendiculars drawn at right angles to the varying directions of the wind must intersect each other at points more distant than the actual central point of the cyclone itself.