TABLE OF CONTENTS. Change of the Yearly Resultant Direction of the Wind from Year to Year Observed Mean Velocities of the Wind. General Changes of the Wind for the Year Relations of the Pressure and Temperature of the Air under different Winds. [xi] & [xii] Amounts of Rain collected in Four Gauges [xii] Relation of the Amounts of Rain which fell under different Winds in 1874 [xii] [xii] Quantity of Ozone under different directions and under different Velocities of the Wind Comparison of Schönbein's and Moffat's Ozonometer. APPENDIX.-Mean Monthly and Yearly Values of Pressure and Temperatures of the Air and of Evaporation for 20 Years (1855 to 1874), and of the Rain for 25 Years (1851 to 1875). RESULTS OF OBSERVATIONS IN TABULAR ARRANGEMENT. Daily Results of Meteorological Observations Readings of a self-registering Max. and Min. Thermometer above the Comparison of Mean Monthly Temperature above the Tower with that near the Surface of the Ground Readings of a Dry Bulb and a Wet Bulb Thermometer placed above the Simultaneous Readings of the Standard Thermometer, and of that by [25] to [29] Characteristics of the Weather in each Month [30] to [32] DIURNAL INEQUALITIES OF MEAN MONTHLY METEOROLOGICAL ELEMENTS ; [33] [34] TABLE I.-Mean Monthly Heights of the Barometer for every Two Hours TABLE IV.-Mean Monthly Temperature of the Air for every Two Hours [36] [36] [37] HYGROGRAPHIC RESULTS. [38] TABLE VII.-Mean Monthly Temperature of Evaporation for every Two TABLE VIII.-Values of the Constants in the Periodical Expression for the Mean Monthly Diurnal Inequalities of the Hygrographic Results [38] TABLE OF CONTENTS. TABLE IX.-Excess of the Mean Monthly Temperature of Evaporation at Page [39] [40] [41] [41] [41] TABLE XIII.-Mean Bi-Horary Horizontal Velocities of the Wind for each Formula for the Mean Yearly Absolute and Relative Velocities of the [42] [42] TABLE XV.-Principal Changes of the Wind [43] to [47] TABLE XVI.-Relations of Pressure, Temperature, &c., under different TABLE XVII.-Amount of Rain collected on the Ground, and at Elevations of 22 feet, 24 feet, and 112 feet [52] TABLE XVIII.-Fall of Rain at the Surface of the Ground distributed under different Winds, for every Month of the Year [52] TABLE XIX.-Indications of Moffat's Ozonometer during the Year [53] [54] TABLE XXI.-Amount of Ozone under different Daily Velocities of the 1. Mean Monthly Heights of the Barometer for 20 Years (1855 to 1874) . [56] [57] [58] [59] INTRODUCTION TO THE ASTRONOMICAL OBSERVATIONS OF 1874. SECTION I.-Personal Establishment; Instruments; and Subjects of Observation. PERSONAL ESTABLISHMENT.-No change whatever occurred in the personal establishment of the Observatory during the year 1874; Mr. John Lucas, as before, occupying the post of First Assistant, Mr. Gabriel Keating that of Second Assistant, and Mr. Frederic Bellamy that of Third Assistant. Mr. William Luff, was, as before, computer to the Establishment, and was occupied chiefly with the reduction of the observations of zenith-distance made with the Transit Circle. Mr. Lucas took charge, as in preceding years, of the Photographic Meteorology, and performed a great portion of the reductions, as is more particularly mentioned in the Introduction to the Meteorological Observations. He has also, in general, charge of the reading of proof-sheets both for the astronomical and the meteorological observations. The reductions of the transit observations with the Transit Circle were performed mainly by Mr. Keating assisted by myself, while those of the Occultations of Stars by the Moon were made by myself, and the Measures of Double Stars, &c. with the Heliometer, were reduced by Mr. Bellamy. Mr. Bellamy assisted both in the astronomical and meteorological departments, and occasionally took part in the astronomical observations, the observations and drawings of solar spots which were commenced in November being made by him, as were the greater portion of the observations of Coggia's Comet. INSTRUMENTS.-The meridional instrument in use is the Carrington Transit Circle, which was purchased of Mr. Carrington and mounted in the west transit room of this Observatory in the summer and autumn of the year 1861. For a detailed description of it and its collimators, and the apparatus connected with it, I beg to refer to preceding volumes. In this place it will be sufficient to state that the instrument is (on a much smaller scale), similar in its general construction to the transit circle at the Royal Observatory, Greenwich. The microscopes, eight in number (though four only are in ordinary use), have the same conical arrangement, and the webbing of the north and south collimators is exactly similar. The object-glass is of 5 inches. aperture and of 66 inches focal length; and that of each collimating telescope is of 2 inches aperture and of 33 inches focal length. Each circle is 42 inches in diameter, the one under the microscopes being bevilled as in the case of the Greenwich Circle. There is a moveable frame for carrying the mercury-trough for reflexion-observations of stars, and the nadir-point is observed by means of a fixed trough supported on a small isolated brick column. The instrument has been used for meridional observations throughout the year, the principal subjects of observation being:-1st, the stars RADCLIFFE OBSERVATIONS, 1874. b which remained unobserved of the British Association Catalogue, as in the preceding year; 2ndly, a considerable number of Struve's Double Stars which have been observed with the Heliometer; and, 3rdly, a selected list of stars compiled by T. Warner, Esq., of Brighton, from the 7th to the 8th magnitudes, lying in a zone between 50° and 53° N.P.D. The Transit Instrument.-This instrument was in use till the end of the year 1861, when it was replaced by the Transit Circle. It was removed from the west to the east transit room in September 1861. It is kept in good condition, and is available for any purpose for which it may be required, and especially for practice of students of the University. A description of it will be found in vols. I and IV of the Radcliffe Observations. The Meridian Circle.-This instrument was also thrown out of use at the end of 1861, and is also available for purposes of instruction. It is fully described in vol. I of the Radcliffe Observations. The other available instruments belonging to the observatory are, 1st, the Heliometer, of which a description will be given farther on; 2nd, a telescope of 10 feet focal length and 7 inches aperture, mounted equatorially on a stone platform south of the observatory, and used in connexion with a journeyman clock striking at the termination of each minute; and, 3rd, a 42-inch achromatic tele-cope, by Dolland, with triple object-glass of 3 inches. There is also a smaller telescope unmounted, of 21 inches aperture, which has occasionally been used in former years. The ancient instruments out of use consist of two brass 8-foot quadrants by Bird, and a 12-foot zenith-sector, in connexion with which may be mentioned an old barometer by Bird. There is also a 10-foot Newtonian telescope by Sir W. Herschel, of which the stand was repaired not long since. Mention must also be made of a large Gregorian telescope made by Short in the year 1750, with object-mirror 18 inches in diameter. This telescope had lain for several years out of sight in the photographic room, and it appears certain from some experiments which have been made with the mirror unmounted, that its figure will require correction, and that it must be re-polished, before any good use can be made of it. The principal clocks belonging to the observatory are four in number; namely, two with mercurial compensation pendulums, by Dent, used with the transit circle and the heliometer; and two with gridiron pendulums, the first of which, by Shelton, was for many years in the apartment of the meridian circle, and the second, by Hawting, in the east transit room. Recently, however, their places have been exchanged; Shelton being put into the east transit room. The three first mentioned are excellent instruments; the last is an old clock, (still useful,) but of an inferior character. There is also a clock with wooden pendulum, which stands in the central hall, and serves to give time for the regulation of ordinary business. A pocket chronometer by Hardy, adjusted to mean solar time, was formerly used for comparison of clocks and for occasional observations. An excellent box sidereal chronometer by Dent was purchased, in May 1868, of the executors of the late Rev. William Rutter Dawes, and is a very useful addition to the observing apparatus, being now constantly employed for the comparison of clocks. The barometer ordinarily used with the transit circle is by Newman, and has a fiducial point, which is brought into contact with the surface of the mercury; that used formerly with the heliometer is by Jones, and has a bag and float for the adjustment of the level of the cistern. Newman was used till July 3, when it was injured by an accident, and was not brought again into use till the end of the year 1874, Jones being used in its stead. Subjects of Observation.-The stars observed with the Transit Circle in preceding years were taken from a compiled list extracted from the British Association Catalogue, including all below the fifth magnitude which are visible at Oxford, and which had not been satisfactorily observed either at Greenwich or Oxford. In the year 1866, this list was supplemented by others taken from Struve's Catalogue of Double Stars, and from various catalogues, in a zone of about 20° in breadth extending from 50° to 70° of N.P.D.; and, in the year 1871, another extension-list, referred to in the preceding page, was added. The sun and the planet Mercury have been observed, and the moon within the limits of the observing hours, which extend from six o'clock to midnight during the winter months, and from dusk to 13h during the summer months. Venus was also observed frequently, chiefly for the purpose of obtaining a reliable value of her diameter; Jupiter and Saturn were also observed from the opposition, and a few observations were made of Uranus and Neptune. The observations with the Transit Circle were made chiefly by Mr. Lucas and Mr. Keating, their initials being Land K; Mr. Lucas, however, confining himself chiefly to observations of N.P.D., and especially to reflexion-observations for the determination of the zenith point: Mr. Bellamy's observations are distinguished by the initials F.B. The Heliometer, which will be described in a following Section, was used by myself and Mr. Bellamy chiefly for the observation of double stars. The stars observed were principally a list of binaries selected from the catalogue compiled by A. Brothers, Esq. The instrument has also been made use of for the observations of occultations of stars by the moon, and phenomena of Jupiter's satellites. SECTION II.-Reduction of the Observations of Right Ascension, made with the Transit Circle in the Year 1874. The observations of Right Ascension, as before stated, were made chiefly by Mr. Keating. The designations of the stars observed follow the same rules as in preceding years. For stars in the Nautical Almanac the names there given are preferred to all others. For stars contained in Baily's Flamsteed, the Greek or Italic letter of Bayer there adopted is used, or, in defect of that, Flamsteed's number, with the name of the constellation. For other stars, the British Association Catalogue is preferred for an obvious reason to all other catalogues; and then, in order of preference, the Catalogus Generalis of Struve (for anonymous double stars), Piazzi, Groombridge, the two Radcliffe Catalogues, |