1. Preface to The Elements of Astronomy (1819).
This Work has been printed for the use of the Students in the University. But as it may fall into the hands of some, not aware of this circumstance, who may expect many things, which are not found in it, and may also meet with others, some of which may not appear proper, and some not sufficiently illustrated, for an elementary treatise, it is necessary to give an explanation as to these.
A complete treatise on astronomy should abound with examples: but in a treatise merely designed to teach the outlines of the science, and to point out what may incite further inquiry, they are not required.
It is obvious that, in the necessarily restricted portion of time allotted to the science of Astronomy in the course of an University Education, a multitude of examples would, to the mass of students, be useless. Therefore it would have been quite improper to have increased therewith the size of this volume, which, at the desire of the College, has been drawn up for their use. Indeed it may be said, that more matter has been introduced than was necessary, Indeed it may be said, that more matter has been introduced than was necessary, that it was unnecessary to introduce the subject of Astronomical Instruments. To this it is answered, that by introducing them as the Author has done, he has endeavoured to benefit the student, and to assist himself. In his annual lectures, he 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 to be found in these elements, enables him to give, with much greater effect, a more minute explanation.
It may not be improper to mention, that most of the substance of this treatise, according to the present arrangement, has been given by the author, in annual lectures since the year 1799, and that the first sixteen chapters have been in the hands of the Students of this University since 1808, having been then printed for their use.
The Student who looks for a more extended knowledge of plane Astronomy, and desires to familiarise himself with astronomical computations, cannot be at a loss for assistance. The work of Professor Vince on practical Astronomy, and the complete system of Astronomy in three volumes, by the same author, will afford him ample information. Mr Woodhouse has also recently published a treatise on Astronomy, in which the most interesting parts of plane Astronomy are minutely explained and illustrated by sufficient examples. The different publications under the sanction of the board of longitude, more particularly the nautical Almanac, will also furnish essential practical information to the Student who desires it. Besides these, and other valuable British publications, he may avail himself of a multitude of works of foreign writers on this subject. Several works are occasionally referred to, and perhaps references should have been oftener made.
The works on Trigonometry are so numerous, and the applications of it are 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 Vince and of Mr Woodhouse 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.
On account of circumstances unnecessary to be stated here, the preface of the former edition, published in 1813, has been reprinted as above. Since that publication Astronomic Theorique et Pratique, par M Delambre, (3 vol. 4to.) has appeared. This work contains very complete details of the application of Trigonometrical Formulas for obtaining results convenient for calculation, and abounds with other valuable matter. Mr Woodhouse has also lately published his second volume, containing physical Astronomy. By this the student may easily become master of many of the important discoveries in physical Astronomy, and may easily prepare himself for the most abstruse investigations in that science.
It was expected that an opportunity might occur of again mentioning the subject of the parallax of the fixed stars. The observations lately made at our Observatory, part of an intended extensive course for re-examining this interesting question, confirm in the strongest manner those heretofore made. No doubt seems to remain that the changes observed are not occasioned by variations of refraction, or by any change in the instrument. They are explained by attributing a visible parallax to certain stars; and observations that have been made elsewhere seem by no means sufficient to overturn this conclusion. At present the question appears to require further examination by means of right ascensions. The differences of right ascensions of stars twelve hours distant from each other seem well adapted for this purpose, and it is hoped that such observations may be made with good instruments in climates more favourable for observations of this kind than ours. With us it seldom happens that two observations, depending on each other, can be both made when separated by an interval of several hours.
2. Preface to Brinkley's Astronomy (1871).
The Elements of Astronomy of Bishop Brinkley has for more than sixty years been used as a textbook by the Students of the University of Dublin. When Dr Brinkley held the office of Andrew's Professor of Astronomy, he delivered the substance of this work, in his public annual prelections to the Undergraduates, from the year 1799 to 1808. In the latter year, at the request of the Board of Trinity College, he printed these lectures in a volume, and afterwards added an appendix of problems. Since that time the work has formed an important portion of the course of study prescribed for the Undergraduate Lectures and Examinations, yet very little alteration had been made in the text to correspond with the recent progress of Astronomical Science. The author had intended to prepare some additions to the work, particularly on the subject of double stars and comets, but was prevented by his episcopal duties, and a distressing and tedious illness. It was long felt by those who were engaged in the teaching and examining of the Students, that while the plan of the treatise was excellent, and admirably adapted for the intellectual training of the Undergraduates, it was in many respects seriously defective as a textbook.
There were many points in the reasoning which, although sufficiently dear to a thinker of Dr Brinkley's ability, required much further elucidation before they could be made intelligible to the ordinary Student. Very important subjects connected with the science were omitted altogether, and in recent times it was universally felt that the treatise was not in keeping with the advanced state of Astronomical Science. The Provost and Senior Fellows of Trinity College, having had reason to believe that the work required considerable improvements, if it were to be continued as a text-book for all Students, and not wishing that a treatise so long and intimately connected with the studies of the University of Dublin should be superseded, commissioned me to undertake a thorough revision of it, and to endeavour to make it suitable to the requirements of the Students and to the present advanced state of the Science.
For this purpose I placed myself in communication with my friend Dr Brünnow, the present eminent successor of Dr Brinkley in the chair of Astronomy; and the valuable assistance which he promptly afforded very much aided me in my attempt to produce a textbook which a long experience as College Tutor enabled me to see would meet the wants of the Students.
The whole of Br Brinkley's work has been carefully revised, corrected, and in many places altogether rewritten. Some considerable portions of the book which were found to be unsuited to the Students have been omitted, while new chapters and portions of chapters have been added which are not to be found in the original work. The arrangement of the chapters has been considerably altered; those which are required of all Students, at the ordinary Term and Degree Examinations, have been placed together. I have written a chapter on the masses of the heavenly bodies and on the Tides, and have also supplied an account of the principal comets, and a method of treating the equation of time different from that adopted by Brinkley, together with numerous other minor additions to every chapter.
Dr Brünnow, besides giving general suggestions, has written new chapters on the physical constitutions of the sun and heavenly bodies, on the discoveries by means of the Spectroscope, on the proper motion of the fixed stars, on the recent methods of ascertaining the parallax of the fixed stars, and on the general advance of Stellar Astronomy. He has also remodelled the portions of the work which treat of instruments, and made them suitable to the present improved condition of practical Astronomy.
I have also endeavoured to substitute new and simpler mathematical demonstrations in many cases where my experience led me to think that the old ones were too cumbrous, and have added a series of questions on the first thirteen chapters which I hope will he found useful to the Students preparing for examinations.
On the whole, it has been my anxious wish to remodel the work of Bishop Brinkley so as to make it correspond with the present extended knowledge of this science, and at the same time to furnish in it such a textbook as my experience as a teacher shows to be required.
I wish to return my best thanks to Professor Brünnow for his assistance, and also to my friend Mr Williamson, for his trouble in reading the proof-sheets, and for his kind suggestions.
JOHN W STUBBS,
Trinity College, Dublin.