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inquiries of Redfield, Reid, Dove, Maury, and others, shew that, capricious as the weather appears to be, it is nevertheless certain that it observes laws as stable and constant as those that govern all other natural phenomena.
The science of meteorology, however, has languished for want of the spirited and pointed aid which is given to other branches of physical inquiry by associated bodies of votaries. Many valuable registers were kept of which the mere numerical mean values were known, while others were entirely lost from want of being classified and reduced. It therefore struck a few amateurs that, in order to secure the advantages of arrangement, publication, and wellconcerted combination, an express association ought to be formed; and accordingly, on the 4th of April, 1850, a meeting of some friends of the science was convened by Dr. Lee at Hartwell; where, in the library, they agreed upon a general system of observation, uniformity of registry, systematic communication, and other measures for insuring precision, to the advancement of the aëro-statical branch of physics. At this decisive meeting, the gentlemen present elected Samuel Charles Whitbread, Esq. of Cardington, near Bedford, as their President, appointed an efficient Council, and thus established the present British Meteorological Society. The aim and principal objects contemplated were thus enumerated :
1. A collection of correct manuscript observations. 2. The publication of tables. 3. The reluction of observations to useful results. 4. A collection of all observations of the same phenomena. 5. The formation of a repository to which observers may consign the results of their labours. 6. The distribution of meteorological papers. 7. The examination and correction of meteorological instruments. 8. The encouragement and promotion of meteorological science.
By turning to page 15 of this work, the reader will see that Dr. Lee had already carefully kept some very creditable barometrical and thermometrical registers; and that an improved system of observing and recording meteorological phenomena had been introduced at Hartwell by Mr. James Glaisher, F.R.S. The instruments now relied upon are as follows:
1. The BAROMETER is a standard one, made by Barrow under the superintendence of Mr. Glaisher. It is of brass throughout, the scale is divided to (in.005, and terminates in a conical point of ivory, which in observation is made to touch the surface of the mercury in the cistern, and the contact is very readily seen by the reflected and the actual point appearing just to meet each other. The vernier subdivides the scale divisions to Oin.002; it is moved by its rack and pinion till the ray of light passing under the back and front parts of the semi-cylindrical plate carried by the vernier appear just to touch the convex surface of the mercury in the tube.
The tube is (in.32 in diameter, the mercury has been boiled within it; the correction for the effect of capillary attraction is therefore (in.013 to be applied additionally. The cistern is of glass. This instrument is recorded every day at 9 A.M. and at 3 P.M. At the top of the instrument are three screws, turning in the fixed part of the support for adjustinent to verticality: and the readings of the barometer are all too low by Oin.002 as determined by Mr. Glaisher. All observations of this barometer are increased by (in.013 for capillarity, and by Oin.002 for inside error, and they are also corrected for the difference of temperature of the mercury in the tube at the time of observation from 32°, by the application of the corrections contained in the table for barometers whose scales are engraved upon brass reaching from the level of the mercury to the vernier. In practice one correction only is needed, a special table having been formed based upon the three necessary corrections.
II. The DRY BULB THERMOMETER is mercurial; its scale is divided to 1°. Its index errors have been determined by Mr. Glaisher. This instrument is read every day at 9 A.M. and 3 P.M.
III. The WET BULB THERMOMETER is mercurial; its scale is divided to 1°. Its index errors have been determined by Mr. Glaisher. The bulb is covered with a piece of fine muslin, and near to it, but distant from the dry bulb thermometer, is placed a small cistern of rain or distilled water. A piece of cotton lamp-wick is connected with the muslin, and its end dips into the cistern of water; the water by capillary action ascends, and keeps the muslin on the thermometer constantly wet. This instrument is read every day at 9 A.M. and at 3 P.M.
IV. The MAXIMUM AND MINIMUM THERMOMETERS: the self-registering thermometer for maximum temperature of the air is mercurial, with a transparent bulb; its index is a piece of blue steel wire. Its scale is divided on box wood to 1°. This instrument is read every morning at
° 9 A.M.
V. The MINIMUM THERMOMETER: the self-registering thermometer for minimum temperature of the air is of alcohol, with a transparent bulb: its index is glass, with a knob at each end. Its scale is divided on box wood to 1°. This instrument is read every day at 9 A.M.
POSITION OF THE THERMOMETERS. At the distance of 58-5 feet south of the house, and on a grass plot, is fixed a post, which carries a revolving frame, similar in its construction in every respect with that at the Royal Observatory at Greenwich. This frame consists of a board four feet one inch and a half wide at the base, and of another board one foot eight inches high, connected with one edge of the horizontal board, and projecting upwards; and of two parallel inclined boards, separated from each other by three inches, meeting the other edge of the horizontal board, and the top of the vertical board. Upon the face of the vertical board are placed all the thermometers in such manner that their bulbs project below the vertical board, and at about four feet above the ground. Above them is placed a projecting roof, to protect them from the effects of radiation and rain. The frame is always turned round after every observation, so that its inclined side is turned towards the sun.
VI. The Rain GAUGE is a simple cylinder gauge, eight inches in diameter, and therefore having an area of 50•3 square inches. The height of the cylinder is thirteen inches and a half; at the depth of half an inch from the top, within the cylinder, is fixed a funnel (an inverted cone), of six inches perpendicular height; with the point of this funnel is connected a tube, one-eighth of an inch in diameter, and half an inch in length; a quarter of an inch of which is straight, and a quarter of an inch is bent upwards. By this arrangement the last drop of water remains in the bent part of the tube. The upper part of the funnel, or base of the cone, is made to touch the internal part of the cylinder all round, and it is believed that evaporation is totally prevented. The cylinder is sunk eight inches in the ground. The quantity of water collected is read at the end of every month.
VII. In addition to these instruments, a standard thermometer is placed on the revolving stand, so that, in the event of an accident happening to the dry bulb thermometer, the series of observations would be continued unbroken; and duplicate instruments of all kinds are kept for the same purpose, and nearly all of which have been examined and their index errors determined by Mr. Glaisher.
On every day from the observations at 9 A.M. and also from those taken at 3 P.M. the true length of the column of mercury supported by air, and that portion supported by water mingled with the air, are determined, as well as the true temperature of air, evaporation, and the dew point; the weight of a cubic foot of vapour, the additional amount of vapour required to saturate a cubic foot of air, the degree of humidity, and the weight in grains of a cubic foot of air under its then pressure, heat, and humidity, are determined. All these hygrometrical results being calculated by the use of Glaisher's hygrometrical tables.
The average monthly and quarterly values of all these elements are determined, and they are published quarterly in the Reports of the Registrar General: and the whole of the instruments are frequently examined by Mr. Glaisher, who also examines all the meteorological work in progress.
Such is the HARTWELL OBSERVATORY; and such is the nature of various praiseworthy establishments which have lately sprung up in England. May success attend them; for, while they act as an incitement to our public observatories, they are each liable to polish some particular scientific gem. And, beside the positive utility of making and reducing observations, surely nothing can contribute more to the elevation of thoughtful reasoning, and the intellectual
intelligence of man, than the contemplation of the wonders revealed by the OMNIPOTENT; albeit our perceptions can only trace by faint shadowings the vastness of his power and glory. Much is certainly now known; but higher views are in all probability attainable, if the various ramifications of knowledge are perseveringly and properly pursued. It is, in the present day, more obvious than it could have been to Pope, that