10-24-357 THIS work is altogether designed for the use of students in the Dublin University, but as it may fall into the hands of some not aware of this circumstance, and who may expect many things not found therein, and may meet with other things to them apparently unsuitable, or insufficiently illustrated, it is necessary to give some explanation. A treatise on astronomy professing to be complete, ought, in the first place, to abound with examples. In a treatise, however, merely designed to teach the outlines of the science, and to point out what may incite and lead to further inquiry, such examples are unnecessary. In the necessarily limited portion of time devoted to astronomical science in the course of a University education, a multitude of examples would, to the mass of students, be perfectly useless. It would be, therefore, improper to increase thereby the size of this volume, which has been prepared at the request of the college for their use. Again, it may be said, that more matter was introduced than was absolutely necessary; that it was unnecessary, for instance, to introduce the subject of astro nomical instruments. It may be answered in reply to this, that their introduction is not only a benefit to the student, but an assistance to the Astronomical Professor. The latter, in his annual lectures, has an opportunity of explaining and illustrating the uses of the different instruments used in the practice of astronomy, to which lectures the students have free access; and the short preparatory account of the instruments given in this volume enables him to give, with much greater effect, a more minute explanation. It may not be irrelevant to mention, that the greater part of the substance of this volume, according to its present arrangement, has been given by the author in his annual lectures since the year 1799, as Professor, and that the first sixteen chapters have been actually in the hands of the students since 1808, having been then for the first time printed for their use. The student who is anxious for a more extended knowledge of plane astronomy, and is desirous of familiarizing himself with astronomical computations, can be at no loss for assistance. The works of Professors Vince and Woodhouse will afford him very extensive information. The different publications, too, under the sanction of the Board of Longitude, more especially the Nautical Almanack, will furnish essential practical aid to the student who desires it; besides these and other valuable British publications, the student may avail himself of a multitude of foreign works on the subject of astronomical science. The transactions of learned so cieties, both at home and abroad, constitute a third very extensive source of information on this subject. Works on trigonometry are so numerous, and its applications so readily referred to, that in common instances it has not been thought necessary to particularize any author. In the Appendix, for which a more extended knowledge of trigonometry is necessary, the treatises of Professor Woodhouse and Mr. Luby have been quoted. These works will be found quite sufficient for obtaining the preparatory knowledge of trigonometry necessary for the more difficult parts of astronomy. The author had intended to prepare some additions for this work, particularly on the subject of double stars and comets, and on the temperature of the earth and its variations. His distressing and tedious illness, with the harassing duties of his ministry, unfortunately prevented him from fulfilling this intention. It is now too late, with regard to the present edition, to think of supplying the deficiency. The knowledge of scientific men on the subjects alluded to is moreover still in a very imperfect state, and the discussion of them may therefore be fairly reserved for a future edition. For a highly interesting detail of all that has been done in these matters, as well as of the nature of the questions themselves, and the various modes of subjecting them to the tests of observation and calculation, the reader is referred to the astronomical treatise in Lardner's Cyclopedia, by Sir J. Herschel. ADDENDA ET CORRIGENDA. Page xvii. line 18, insert commas after the words "moon" and "planets." 12, for in read on. 4, The interposition of large opaque bodies revolving about them is assigned by Laplace as another explanation of this pheno menon. 23, for precison read precision. 17. This law of Professor Bode would also fix a planet at the earth's distance from the sun, and thus it affords an argument for the earth's annular motion. Similar laws have been shewn by Mr. Challis of Cambridge, to exist for the satellites, thus for Jupiter's satellites, for example: 102, See Cambridge Phil. Trans. vol. iii. 17, for 1834, read 1835. By the calculations of Pontecoulant and Damoiseau, the return of this comet to its perihelion was fixed, by the former to the 7th, and by the latter to the 4th of November, 1835. 15, for neighburhood read neighbourhood. 109, 139, 24, for polaris 0h 54'37" read a polaris Oh 54m 37%. ... 17, for a second, read half a second. 15, for 20 years, read 30 years. 14, for Pb read Pz. 20, for (art. 116) read (art. 110.) 9, for r' read p'. 158, 177, 257, 258, 260, 262, 15, for sin read sin SP. 10, for r't read rt'. |