ON the 25th of October last The Times published for the first time a remarkable alteration in its usual daily chart of the barometer, and considering the import- ance of the subject, we append its intro- ductory remarks, and also an exact copy of the illustration of the barometer chart as it appeared on the above-named day.

"We commence publishing to-day the indica- tions of this barometer, reduced to mean sea level, and corrected for temperature. Our first edition will contain the heights of the column of glycerine at intervals of two hours, from 2 P.M. to 2 A.M., according to the actual scale readings of the in- strument; and in pur second edition will be similarly given the indications from midnight to noon. Our readers will thus have vividly brought before them the fluctuations of pressure constantly taking place in the great atmospheric ocean at the bottom of which we live. Insignificant as these fluctuations may seem to the uninformed, it is impossible to over-estimate their real importance.

A fall or rise of one-tenth of an inch in the mer- curial column attracts little attention, and is apt to be thought of no consequence; but when the same causes are shown to make a difference of more than an inch in the height of the glycerine column, no intelligent person can fail to be im- S ressed by their meaning. We still know very ttle about the vibrations of atmospheric pressure, because to a great extent the minute scale of the mercurial barometer has placed great difficulties in the path of meteorological students. Admirable and convenient as that instrument is, the want of an atmospheric balance, constructed with a fluid of lower density, so as to give a wider direct range of movement in the column, has long been felt. In 1830, Professor Daniell made for the Royal Society a water barometer, but the effect of changing temperatures on the water vapour in the Torricellian vacuum masked the indications of varying pressure, and the attempt failed. Other experiments in the same direction gave similar unsatisfactory results, and it was not until Mr.

Jordan, of the Museum of Practical Geology, in Jermyn Street, constructed his glycerine barometer that the problem, simple as it appears, could be considered solved. The boiling-point of glycerine is 440 F., and a very low temperature is required to solidify it. It has, therefore, a very low ten- sion of vapour at ordinary atmospheric tempera- tures, and these only produce changes in the length of the glycerine column by expansion or contraction of the liquid itself. The specific gravity of pure glycerine is 1-26, or less than one-tenth that of mercury; so that the mean height of the glycerine column is 27 ft. at sea level.

A variation, therefore, of one-tenth of an inch in the height of the mercurial column is shown on the glycerine, as already stated, by a variation of more than an inch, and with this vastly increased range and visibility and sensitiveness, the only serious drawback found by Mr. Jordan was the tendency of glycerine to absorb moisture from the atmosphere. He ingeniously overcame that de- fect by covering the surface of the liquid in the barometer cistern with a shallow layer of heavy petroleum oil, thus neutralizing its absorbing ten- dency, while the atmospheric pressure remained intact. The tube forming the body of the instru- ment is an ordinary composition metal gas-pipe, three-eighths of an inch internal diameter, and furnished at the top with a gun-metal socket, into which is cemented a glass tube 4 ft. long, and having an inside diameter of one inch. The upper end of this glass tube is formed in the shape of an open cup, fitted at its neck with an indiarubber stopper. In this tube the fluctuations of the top of the column are observed, and the height read off on brass scales placed on either side of the tube, and fitted with indices and verniers, moved by milled heads. The scale on the right-hand side is divided into inches and tenths of absolute measure, numbered from the level of the liquid in the cistern, while that on the left shows equivalent values reduced to a column of mercury, and divided into tenths and hundredths, each hun- dredth being equal to about l-10th of an actual inch. The main tube, 27 ft. long, is connected at the base with a copper cistern, tinned inside, 5 in.

deep and 10 in. in diameter. This cistern is fitted with a screwed cover, through a small hole in the cup of which the air has access, while cotton wool is used for filtering out dust. The glycerine, coloured red by aniline, and heated to a tempera- ture of 100 F. to render it limpid, is poured into the cistern. By means of an air-pump connected to the top of the glass tube, the air in the tube is exhausted, and the liquid is raised therein by atmospheric pressure to a height of 322 • 571 inches, equivalent to 30 inches of mercury. The plug of the cistern is then screwed in its place to support the column, the pump connections removed, and the air admitted at the top. A sufficient quantity of glycerine to fill the tube being poured in from above, the indiarubber stopper is inserted. The screw plug of the cistern being removed for a few seconds to allow the column to fall an inch or two and then replaced, the instrument is now allowed to rest until all traces of air in the liquid have ascended into the Torricellian vacuum. Then the indiarubber in the top cup is again withdrawn, and the tube finally filled up with glycerine, when, the screw plug in the cistern being withdrawn, the column gradually falls until balanced by the pressure of the atmosphere. A small quantity of glycerine left in the cup above the indiarubber stopper, with a plate-glass cover on the top to keep out the dust, hermetically seals the vacuum and completes the arrangement. One of these barometers has been constructed at the Kew Observatory, the Royal Society Committee devot- ing a small grant from the Government fund at its disposal for the purpose. Another has been placed in the Museum of Practical Geology in Jermyn Street. There is a third in operation at South Kensington, and the fourth is now in operation at this office. It seems unquestionable that an in- strument of this kind is admirably suited for practical use at meteorological stations, at sea- ports, in collieries, and in all other situations where it is of importance for the unpractised eye to notice frequently and easily the changes taking place in atmospheric pressure." The subjoined Diagram gives the indications at intervals of two hours from 2 P.M. to 2 A.M. of the Jordan Glycerine Barometer in use at this Office, the readings being corrected for temperature and reduced to mean sea level.

j~, 2 p.m. 4 p.m. 6 p.m. 8 p.m. 10 p.m. M. 2 a.m.

s an- • « 4 * _j « 1 1 1 I The National Life-boat Institution has one hundred and twenty barometers on the coast, whose indications during un- settled weather are carefully and anxiously watched by our seafaring population and others. All these instruments are of a standard class, and accordingly are im- plicitly relied on. In fact, they forecast weather with no uncertain sound, and thus these one hundred and twenty baro- meters hare no doubt contributed to the saving of a large number of lives, and of much property, by distinctly and oppor- tunely warning our seamen and fishermen of the coming storm, which, if unheeded, might often have proved destructive, both to their lives and property..