« ElőzőTovább »
THE SOCIETY FOR THE diffusion OF USEFUL
FOR THE YEAR
Chairman-H. BROUGHAM, Esq., F.R.S., M.P.
Vice Chairman-LORD JOHN RUSSELL, M.P.
James Morrison, Esq.
Treasurer-WILLIAM TOOKE, Esq., F.R.S.
Rt. Hon. J. Abercrombie, M.P.
Rt. Hon. Lord Auckland.
Hon. G. A. Ellis, M.A., M.P.
Ashburton J. F. Kingston, Esq. Birmingham Local Association.
Rev. John Currie, Chairman.
Rev. Prof. Henslow, M.A.,
Rev. Leonard Jenyns, M.A.,
Rev. John Lodge, M.A.
F.R.S. & G.S.
Leonard Horner, Esq., F.R.S.
Henry B. Ker, Esq., F.R.S.
J. Marshall, Esq., M.P.
D. Ellis, Esq., F.R.S.
J. Marshall, Jun., Esq.
Dr. Traill, Chairman.
J. Mulleneux, Esq., Treasurer. Rev. W. Shepherd. J. Ashton Yates, Esq. Maidenhead R. Goolden, Esq., F.L.S.
Rt. Hon. Lord Nugent, M.P.
T. Spring Rice, Esq., M.P., F.A.S.
C. E. Kumbold, Esq., M.P.
Rt. Hon. Lord Suffield.
J. Whishaw, Esq., M.A., F.R.S.
THOMAS COATES, Secretary, 4, South Square, Gray's Inn.
PUBLISHED BY CHARLES
13, PALL-MALL EAST.
Price Two Shillings and Sixpence, stitched in a wrapper.
W. CLOWES, PRINTER, STAMFORD-STREKT.
Are kept on sale at the Office of Publication, and may also be obtained of the Book-
Explanation of the column "Remarks on the Weather."
THE principal observations consist of the average or mean state of the atmosphere in the different months in regard to pressure, temperature, and moisture; and of the extremes to which it is liable in these respects. The Barometer, by which the first is measured, is an instrument now too well known to require description in the limited space to which this explanation must necessarily be contined. The observations are recorded in inches and thousandth parts of an inch of mercury. The Thermometer, by which the variations of heat are ascertained, is also generally known. The temperature registered is that of the air in the shade; but, besides this, the power of the sun's rays is recorded, and the force of terrestrial radiation; which we cannot here further explain than by describing it as the cold produced at night upon a plot of short grass exposed to the full aspect of the sky; where the temperature, in clear and calm weather, is always considerably below that of sheltered situations. The Hygrometer, by which the state of the atmosphere is ascertained with regard to moisture, is not as generally known as the two preceding instruments it is a contrivance by which the degree of temperature is readily noted at which moisture begins to be deposited upon a cold body as we see in summer in the familiar instances of a bottle of wine brought from a cellar, or a decanter of water fresh filled from a well. This degree is called the dew-point; and from it the degree of dryness may be accurately calculated, and the force or elasticity of the atmosphere of steam, which is always mingled with the air.
The mean state of the atmosphere, calculated for definite periods from numerous observations, being that state in which all disturbing causes are equally balanced, may be considered, when it occurs, as least liable to sudden alteration; and whenever, on the contrary, the different instruments indicate an approach to extremes, reason, as well as experience, teach us to expect a change. Rapid alterations, also, are indicative of violent disturbances, and a sudden approach to one extreme is generally speedily followed by a change to the opposite. The averages have been calculated for London; but they will apply to a very large circle around; and we shall hereafter show how they may be corrected for any situation in the United Kingdom.. It would appear scarcely necessary to impress upon any mind acquainted with the commonest principles of science, that the computations which are given in the column of "Remarks on Weather," are averages deduced from long observation; and that, as such, they are not to be mistaken for prophecies, but are simply to be regarded as the basis of useful anticipations, upon the safe principle that like causes produce like effects. Their value is not to be proved by comparing them with the indications of the Barometer, the Hygrometer, the Thermometer, or the Weathercock, during a single year-nor at one particular place. They are AVERAGES of long periods, and do not apply to all places, without certain modifications. We mention this, because a person thus writes to us from Woburn,-"From my constant observations, from the commencement of the year to the present day, I have invariably found your weather table altogether wrong." It would be less irrational if he were to say to the Inspector of Corn Returns,-" From my constant notice of the price of wheat in Woburn market, I find your average prices quite inaccurate." When people have been accustomed to believe in the absurdities of weather prophecies, it is difficult to satisfy them with common sense.
Explanation of the Column of the Position of Stars and Planets. IN the Almanac of this year we have given the position with respect to the horizon and meridian, of the most remarkable Stars and Constellations visible on the first and fifteenth days of every month, at ten o'clock in the evening. If their positions are required for any other day, at the same hour, they may be easily found by a reference to the position on that day of any star or constellation said to be on the meridian, or near to it, on the day nearest to the given day at 10h., in the following manner :-Suppose that the position of the star Spica Virginis is required on the 14th of May in this year: we find, on consulting the Almanac, that a star having nearly the same right ascension* as Spica Virginis is set down as passing the meridian at ten o'clock in the evening on the 15th of May; now as this star passes the meridian of any place about four minutes sooner every night, it will pass the meridian on the 14th, four minutes later than on the 15th, or at about four minutes past ten: therefore, at ten in the evening of the 14th, Spica Virginis will be found 18 minutes distant from the meridian towards the West, and consequently all the other stars, &c. whose positions are given for the 15th, will be, on the 14th, four minutes in time farther towards the East, a distance of no account, when the object is only to identify the star, &c. named. If the reader have in his possession a
*See Catalogue of Greenwich Stars in the Nautical Almanacs; the right ascension of Spica Virginis is there found to be about 13h 15'.