THE TRANSIT OF VENUS.*

Globe, Volume II, Issue 114, 12 October 1874, Page 3

THE TRANSIT OF VENUS.*

Two small astronomical books, written by Archdeacon Stock, and published at the New Zealaud Educational Depository, Wellington, have come into our hands, and as they refer to matters which are just now creating some little stir in this country, we take the opportunity of making some remarks upon them. We shall begin with that which treats of one particular phenomenon, and which is entitled The Transit of Venus, and Horn to Observe It. It is merely a short pamphlet, of a few pages, and, according to its first sentence, it proposes “ to give an account of the forthcoming transit that may be readily understood.” It is, in fact, the substance of a lecture delivered in Wellington last year. Undoubtedly the author of this pamphlet has seized the right moment for putting forth some kind of popular account of the transit of Venus, the means of observing it, and its use. The phenomenon itself is clearly understood, we suppose, hy very few people indeed. A larger number have a vague sort of notion about it, although, if asked to describe or explain it, they would most likely be quite unable to do either. Rut the very great majority, if they have evergiven a thought to the matter at all, probably imagine that we shall in a few months see some wonderfully mysterious, if not startling, appearance in the sky: perhaps an explosion, in which Venus and the sun will be somehow or other mixed up. Either of these two last classes would therefore, if they took any interest in the transit, be grateful for some plain statement which should make it as clear to their minds as such things can be. But it is by no means an easy thing to produce such astatemeut. Of all the pheuomeu i of nature, those which belong to the science of astronomy are the most difficult to re'-der intelligible to persons who are not in the habit of studying them. Occurrences which take place on the earth can usually be fairly reproduced by pictures ; but the heavenly bodies seem so small, their motions are apparently so irregular, and their distances so vast, that diagrams and pictures never can give really clear ideas of them. If, however, the attempt is made to explain astronomical phenomena without the aid of any diagrams the difficulty becomes very much greater. In that case it is necessary that the teacher, if he wishes to make himself clearly understood, should omit none of the processes, so to call them, of his work ; that no inaccuracy, however small, should be allowed to creep in ; that the language used should be as little technical as possible ; and, especially if his exposition is intended for general use, that he should speak as if all his hearers were equally ignorant of the questions on which he treats. We take it for granted that Archdeacon Stock has intended his pamphlet for the instruction of the unlearned as well as for the guidance of those who have some slight knowledge of his subject. The work has therefore to be tried by the tests which we have just laid down, and we are sorry to say that, to our mind, it does not entirely satisfy them all. For instance, we have said that in matters of this kind accuracy is of the first importance. It is probable that the statement in the pamphlet that the distance of Venus from the earth is sixty-six millions of miles is only an error arising from careless revision, but it is one which is calculated to very much mislead a reader not well conversant with the facts. Again, Mistook says that Venus will take say ten hours in crossing the “sun's centre he means, of course, a line drawn through the centre of his disc, but, as it stands the statement is inaccurate. Small things like these detract, as we think, much from the usefulness of a professedly clear explanation. If we apply the test of simplicity the pamphlet is once more found wanting. We have observed that it is difficult to clearly explain astronomical phenomena. This difficulty is more particularly apparent when treating of the transit of Venus, an occurrence in which the sizes and characters of the different bodies are so diverse, and which seems to require a number of processes of calculation of various kinds before the desired result is attained. These calculations have also, so to speak, to be manipulated, t wisted about, as it were, in every direction, until, to an unscientific mind, they seem to form a complete puzzle. Now, in his lecture last year, Archdeacon Stock probably made use of numbers of diagrams which he was naturally enabled to explain to his audience as he went on. He has omitted these diagrams in his pamphlet, the result being that in some places his exposition becomes obscure and difficult to follow. We would instance, as examples of this, the paragraph on page 8 containing the explanation of Del sle’s mode of utilising the transit, and the paragraph on page 10 showing how to deduce the distance of the sun from the observations taken. Roth of these are, no duu-t. cleir enough ui, and easilj understood by, poisons accustomed to such calculations. Rut, as we have already said, we presume that in publishing for general use this pamphlet, the author intended it for the instruction of the ignorant as well as of those who have some slight knowledge. It is, therefore, to be regret: ed that he did not go rather more into delails. Rycutting out all diagrams, and aiming at perhaps too much terseness, he has, we fear, somewhat impaired the efficiency of his work, and in a manner sacrificed usefulness to brevity. Excepting, however, the slight inaccuracies, to some of which we have adveited, the faults of this pamphlet are, after all, but minor ones, and, in fact, may even be useful, as they tend to make the reader employ some slight exertion in order to fully comprehend the subject. The author has certainly chosen the right time for publishing this little work, which we hope may be usefully studied by many readers. We can only regret that he did not think tit to slightly enlarge it. The phenomenon of which it treats, although not one which will very greatly startle, or perhaps impress, ordinary people on the 9th of December next, is yet one which has a very great scientific importance. And we cannot but welcome any attempt to place its character

and use before; the public ns an attempt in the right direction. Archdeacon Stock is well known as a practical aUrenonvr, and we hope to have other opportunities in future of referring to works from his pen, without even the slight animadversions which we have been obliged to make on his present pamphlet, We have, in fact, one other little book by the same author now lying before us. It is called Astronomy for Bejinners, who lire in the Southern 'Hemisphere. The idea is certainly an excellent one, for we dare say that not only learners but teachers of this science in this colony must have often felt at a disadvantage, when seeking explanations of the movements of heavenly bodies from works written by men in Europe. As the author points out in his preface, the difference in the apparent motions of the planets, the change of position, relatively to the observer, of the east and west points, when looking towards the sun, and other variations, usually make it necessary for the pupil to be perpetually reversing in his own mind the positions laid down in the diagrams in ordinary books, a necessity which naturally tends to produce confusion and its natural consequence, ignorance. Mr Stocks’ book is a very short one, and would seem, if we imagined it to be intended as a hook for study , to be open to the same objections as his pamphlet, namely, too great brevity and a want of sufficient clearness. But it is evident, from an examination of its pages, that it is intended more as a guide for teachers themselves than as a lesson book for pupils. In many parts the explanations are so brief that they are clearly meant to be supplemented by verbal teaching. Thus, for instance, in explaining the discovery of the velocity of light, it is plain that the, reader is supposed to know something before he reads the hook, and the diagram appended is not fully described or detailed. We look upon the book, then, more as an aid to teachers than anything else, and in this sense we are glad to be able to recommend it to masters of schools. It is but an inlrodnetion to science, adapted to those who, with a certain knowledge of mathematics, have none of astronomy. For any others it does not go far enough, and no one, probably, starting from knowing nothing of the motions, &c. of the planets and other heavenly bodies, but with a desire to learn, could attain to much acquaintance with them by the help of this book alone. There are, however, many things in Astronomy for Beginners which will bo found useful to schoolmasters. It may, in fact, be looked on as a collection of notes and data, too fragmentary to be useful by themselves, but excellent as a foundation whereon to lay a complete system of study. As the author himself says in conclusion, a little has been told in the hope that the rest, which has not been told, may be learnt. We cordially congratulate Archdeacon Stock on the production of this little book, and we shall not be sorry to meet with him again in a much larger and more elaborate work.