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HA RD WICKE'S SCIENCE- G OSS I P. 



repaying sight he is ! A huge ball, surrounded by 

 rings and attended by a retinue of no less than eight 

 satellites, and who can say that even that large 

 number is not within the truth ? The larger the 

 telescope, the more light we can collect, the more 

 shall we be able to discern in this magnificent object. 

 The ball itself, which is 75,600 miles in diameter, 

 (nearly 14,000 miles less than that of Jupiter), is 

 crossed by many belts and streaks, varying in position 

 and magnitude but always, like those on Jupiter, 

 parallel to the equator. Its axial rotation is 

 accomplished in a little over, and that of Jupiter in a 

 little under, ten hours. In observing such faint 

 objects as the markings on Saturn and on his rings, 

 it is the goodness of the observer's eye that tells as 

 well as the excellence of the instrument. Some 

 persons have much keener vision than others ; the 

 mantle of the "eagle-eyed" Dawes seems to have 

 descended on Mr. Isaac Ward, of Belfast. It must 

 be remembered, too, that it is always easier to see 

 what is known to exist than to make its first discovery. 

 Saturn's rings may well be reckoned among the most 

 wonderful sights in the heavens. What those 

 remarkable appendages consist of no one knows ; in 

 the opinion of some astronomers they are composed 

 of an enormous number of small satellites, so close 

 together that owing to the great interval that separates 

 us from Saturn (his mean distance from the sun is 

 more than 886,000,000 miles), we are unable to dis- 

 cern them as separate objects. Whatever their com- 

 position may be, we know from actual observation 

 that these rings are very thin. For convenience sake, 

 that which is outermost is designated A, the next B, 

 and the next C. The existence of these rings was 

 first made known by the observations of Christian 

 Huygens in 1659. The outside diameter of A is no 

 less than 172,240 miles, and the inside diameter of C, 

 92,000 miles. When the air is very clear and a 

 powerful telescope is employed, A and B are found to 

 have numerous streaks on their surfaces, in fact A is — 

 at any rate apparently — permanently divided by at 

 least one black space, which is not by any means a 

 difficult object even in a small telescope. Owing to 

 the combined motions of the earth and Saturn, these 

 rings present different aspects to us at different times. 

 All the planets do not move in their elliptic orbits 

 round the sun in the same plane. If we were to make 

 an Orrery, or mechanical arrangement to represent 

 the motions of the planets round their primary, it 

 would not be correct to place them in such a way that 

 imaginary lines drawn from the centre of the sun to 

 that of each of the planets should all be horizontal. 

 Some would have to be inclined more, and others 

 less, to this horizontal line, for the orbits of all the 

 planets are not in the same plane. It is, therefore, 

 evident that we shall see sometimes the northern, 

 sometimes the southern, side of the rings, while at 

 other times they will appear edgewise. All the 

 phenomena, from their widest opening, to their 



becoming almost — under some circumstances quite — 

 invisible on account of their edgewise presentation, are 

 gone through for each side of the ring in about fifteen 

 years, that being half the time spent by Saturn in 

 moving round the sun. In certain positions the rings 

 will appear to be almost parallel to the belts on the 

 planet itself, and it is most probably due to this fact 

 that our acquaintance with ring C is of so short a 

 duration. It is not bright, as A and B are, but very 

 faint, and the body of the planet can be seen through 

 it. From this peculiarity it is generally known as 

 the crape or dusky ring. Very little was known of 

 it till it was observed by W. Bond, in America, on the 

 night of November nth, 1850 ; a fortnight later, but 

 before Bond's discovery was known in England,. 

 Dawes saw it. It was not, however, till nearly two 

 years afterwards that the fact of its being transparent 

 was established. Traces of it had apparently been 

 noticed two hundred years previously, but its annular 

 nature was not then established. It is most obvious 

 where it crosses the planet itself, and on this brighter 

 background has been frequently seen with the little 

 one and a half inch object-glass previously mentioned. 

 Few telescopes will show all Saturn's moons in all 

 parts of their orbits. Titan, the largest and the first 

 to be discovered (by Huygens in 1655), is very con- 

 spicuous ; some of the others are exceedingly faint, 

 and their surfaces do not appear to have the same 

 reflecting power. Though anxious to see all that is 

 possible in the Jovian and Saturnian systems, we must 

 remember that a certain amount of light is necessary to 

 ensure good definition. The deeper the eye-piece is, 

 the more contracted is the field and the more con- 

 spicuous and troublesome is any defect in either the 

 telescope or its mounting. We must not, therefore, 

 yield to the temptation of overpressing our magnifying 

 power. Eye-pieces which give a magnification ot 

 about fifty to the inch of aperture will usually give 

 the most satisfactory results, though no absolute law 

 can be laid down. 



Having viewed Mars and the " giant planets " 

 Jupiter and Saturn, which are telescopically the most 

 interesting of their class, we might wish to pursue our 

 investigations and examine the remaining planets. 

 Mercury is best seen in the daytime, for, since his 

 mean distance from the sun does not much exceed 

 35,000,000 miles, he never appears sufficiently far 

 from his primary to be well seen either before sunrise 

 or after sunset. Nor does he with a diameter of 

 only 3000 miles present a large disc. Venus, too, is 

 best seen by daylight, though not entirely for the same 

 reason, for her distance from the sun is more than 

 67,000,000, and her diameter 74S0 miles. Owing 

 probably to some peculiarity in her atmosphere, she 

 reflects so much of the light that she receives from the 

 sun that when she is most brilliant to the naked eye 

 — and she can then be easily picked up by the unaided 

 vision in the daytime, if her position is known — she is 

 not able to be well seen on the darker background of 



