By JAMES GLAISHER, Esq., F.R.S.

THE variations, in the reading,of the barometer at the Royal Observatory, Greenwich, from October 26 to December 6, 1867, are shown in the annexed diagram, together with the directions of the wind and the horizontal movement of the air extending over the same interval of time.

The very extraordinary state of the weather in respect to successive gales of wind of more than ordinary force, not only on our own coasts but also over different parts of the world', and particularly in the East and West Indies, which have been for some time, past causing disasters at sea to be more numerous, and the loss of life to be far greater than usual, give to all correct meteorological observations, wherever taken, a greater value than ordinary. These storms, both in their rise and subsidence, should be traced and studied, particularly with reference to any premonitory symptoms, for some time preceding the storm, such as the state of the air, both in respect to temperature and moisture, in addition to those of the readings of the barometer, in relation to any departure from its normal state by unusual changes of temperature or excess, of humidity. .It is probable (hat for some distance from the equator both these elements may be affected before the marked changes take place in the readings of the barojnet r, and might thus be made available for, longer notice of approaching storms. For #)e recent storms this information must be available ia; fixed observatories in adjacent localities. Great interest attaches to the weather preceding storms; I shall therefore give a few particulars of the weather during..'the period preceding that given by the diagram.

The month of September opened with fine weather. The reading of the barometer on the 1st was 29'70 in., increasing to 29:-97 in. by noon on the 2nd: it then decreased a little till, the 7th, when it was 29-92 in.; it then decreased to 29-63 in. on the 9th, increased to 30-21 in. by the 18th.

From this time till the 22nd, the readings were above the average. On the 22nd it w,as 29-75 in., increasing to 30-33 in., the maximum reading of the month on the 25th, and remaining, above 30 in. until the 30th, when it decreased to 2Q-86 ia. The weather was generally fine throughout the month.

The highest reading of the barometer in October took place on the first day, when it was 30-31 in.; it then decreased to 29-69 in. on the 2nd, increased to 29-99 in.

by noon on the 4th; from this, time till the 7th the readings were nearly stationary, the range being only 200ths of an inch. It then decreased rapidly to 29*40 in. by 9 a.m. on the 8th. This fall was accompanied by a gale of wind. The readings increased from 29-40 in. on the 8th to 20-74 in. on the morning of the 9th, and decreased to 29 -45 in. on the evening of the same day.

The readings then increased by six-tenths by 9 a.m. on the llth, decreasing a like amount by noon on the 13th, followed by rainy weather, which continued until the 19th; from the 13th the barometer increased to 29'77 in. on the 16th ; the range from the 16th to the 19th was only two-tenths.

The reading was 30-09 in. at noon on the 22nd, decreased to 29-70 in. by the 24th, increased to 30-06 in. by 9 a.m. on the 26th, and decreased to the minimum reading a B a a of the month on the 27th. From the 26th of October all the readings of the barometer are shown in the diagram, together with the simultaneous directions of the wind, and its horizontal movements in miles for twenty-four hours.

For several days preceding the 27th of October, the pressure of the wind had been very small, and during the early morning hours of that day (midnight to 9 a.tn.), the pressures varied between 3 Ibs. and libs.: after 9 a.m. the wind increased in violence, and blew with forces varying between 2 Ibs. and 17 Ibs. till Oh. 40m. p.m.

The gale then increased, and culminated in violence at I'15p.m. during a very heavy shower of rain, the extreme gust recorded At that time (30 Ibs.) coinciding with a sudden turn of the vane from S.S.W. to N.

After the extreme gust, the gale subsided almost immediately, and during the remainder of the day little or no pressure was recorded. On the 29th and 30th, pressures were recorded amounting to 8 Ibs. and 11 Ibs. (extremes).

From October 31st to November 6th, light pressures 'were occasionally recorded, When the mean reading was .

Between . . .

barometer 30-45 in.

. SO in, and 30' 4 in.

29-6 in. and 30 in.

;; . . . 29-3 in. and 29- 6in.

And when it was 28'96in.

showing that whenever the barometer reading has been extremely high, the motion of the air has been small; and whenever extremely low, it has been large. It will however be observed, that in intermediate readings, at times the movement has been small, and at other times somewhat large; these apparent exceptions happen generally just before a change in the direction of the wind. As a rale, as the barometer readings decrease, the motion of the wind increases.

In the midst of the desolations of the storms of November and December, it is satisfactory to find some consolation in the determined courage and success of our noble life-boat crews. That the' boats of the NATIONAL LIFE-BOAT INSTITUTION have been doing great work can easily be understood when I mention that, during the gales and heavy seas of tfiese la t two months, they have alone rescued from various shipwrecks two hundred and fifty-nine lives.

Most of them have been the lives of our brave sailors who help to Carry on the commerce of our great country, and who are the and November 6 to 15 was a period of scarcely any pressure.

Severe gales from N.E. occurred on the 16th and 17th, in which frequent pressures were recorded of 10 Ibs., occasional pressures to 15 Ibs., and maximum pressure of 30 Ibs. From the 18th to the 29th the wind blew with little force; but from the 30tb November to the 3rd of December, a succession of gales occurred from S.W.

first and afterwards from N.W. and N.

Extreme pressures in these gales were recorded of 30 Ibs. (especially on the morning of December 2), but the pressures -during the gales were never less than from 41bs. to 12 Ibs.

By collecting the numbers at the foot of the table with the readings of the barometer, beginning with highest, the two highest barometer readings were on November 9 and November 24, and the mean of horizontal movements on these days was 94 miles.

By collecting in like manner all readings between 30 in. and 30 4 in., those between 29'6 in. and 30 in., and so on, the following table is formed— The average daily horizontal movement) „, ,, of the air was about j 9* mlle«- 204 „ 4*3 „" 56'J „ bread-winners of many a home, which, in the absence of these noble life-boat services, - would be to-day the scenes of desolation and woe.

Let us earnestly hope that the labours of the NATIONAL LIFE-BOAT INSTITUTION may continue to. receive the Divine blessing, and that it may be enabled still further to extend its sphere of usefulness.

Blackheath, December, 1867.

JAMES GLAISHER..