The following comments in Smyth's usual pungent style are worth remembering: 'The furor of a green astronomer is to possess himself of all sorts of instruments—to make observations upon everything—and attempt the determination of quantities which have been again and again determined by competent persons, with better means, and more practical acquaintance with the subject. He starts with an enthusiastic admiration of the science, and the anticipation of new discoveries therein; and all the errors consequent upon the momentary impulses of what Bacon terms "affected dispatch" crowd upon him. Under this course—as soon as the more hacknied objects are "seen up"—and he can decide whether some are greenish-blue or bluish-green—the excitement flags, the study palls, and the zeal evaporates in hyper-criticism on the instruments and their manufacturers.'
This is a true sketch of the natural history, or rather, of the decline and fall, of many an amateur observer. But there is no reason why so ignominious an end should ever overtake any man's pursuit of the study if he will only choose one particular line and make it his own, and be thorough in it. Half-study inevitably ends in weariness and disgust; but the man who will persevere never needs to complain of sameness in any branch of astronomical work.
CHAPTER III
THE SUN
From its comparative nearness, its brightness and size, and its supreme importance to ourselves, the sun commands our attention; and in the phenomena which it presents there is found a source of abundant and constantly varying interest. Observation of these phenomena can only be conducted, however, after due precautions have been taken. Few people have any idea of the intense glow of the solar light and heat when concentrated by the object-glass of even a small telescope, and care must be exercised lest irreparable damage be done to the eye. Galileo is said to have finally blinded himself altogether, and Sir William Herschel to have seriously impaired his sight by solar observation. No danger need be feared if one or other of the common precautions be adopted, and some of these will be shortly described; but before we consider these and the means of applying them, let us gather together briefly the main facts about the sun itself.
Our sun, then, is a body of about 866,000 miles in diameter, and situated at a distance of some 92,700,000 miles from us. In bulk it equals 1,300,000 of our world, while it would take about 332,000 earths to weigh it down. Its density, as can be seen from these figures, is very small indeed. Bulk for bulk, it is considerably lighter than the earth; in fact, it is not very much denser than water, and this has very considerable bearing upon our ideas of its constitution.
Natural operations are carried on in this immense globe upon a scale which it is almost impossible for us to realize. A few illustrations gathered from Young's interesting volume, 'The Sun,' may help to make clearer to us the scale of the ruling body of our system. Some conception of the immensity of its distance from us may first be gained from Professor Mendenhall's whimsical illustration. Sensation, according to Helmholtz's experiments, travels at a rate of about 100 feet per second. If, then, an infant were born with an arm long enough to reach to the sun, and if on his birthday he were to exercise this amazing limb by putting his finger upon the solar surface, he would die in blissful ignorance of the fact that he had been burned, for the sensation of burning would take 150 years to travel along that stupendous arm. Were the sun hollowed out like a gigantic indiarubber ball and the earth placed at its centre, the enclosing shell would appear like a far distant sky to us. Our moon would have room to circle within this shell at its present distance of 240,000 miles, and there would still be room for another satellite to move in an orbit exterior to that of the moon at a further distance of more than 190,000 miles. The attractive power of this great body is no less amazing than its bulk. It has been calculated that were the attractive power which keeps our earth coursing in its orbit round the sun to cease, and to be replaced by a material bond consisting of steel wires of a thickness equal to that of the heaviest telegraph-wires, these would require to cover the whole sunward side of our globe in the proportion of nine to each square inch. The force of gravity at the solar surface is such that a man who on the earth weighs 10 stone would, if transported to the sun, weigh nearly 2 tons, and, if he remained of the same strength as on earth, would be crushed by his own weight.
