When the young have toads, they push open

which is closed by a sort of lid. grown to the condition of little the lids of the pits and swim out of their mother's back. Specimens of these toads, with the eggs and young, in various stages, embedded in their mother's back, are to be seen in most museums of natural history. Toads and frogs catch their prey by throwing forward the sticky tongue which is attached near the front of the lower jaw, and so lick up their victim with startling abruptness. The Cape frog of South Africa (Xenopus), like the Surinam toad (Pipa), has no tongue, and is also remarkable for possessing hard, pointed ends to its toes. It rarely, if ever, leaves the water.

TH

XXIII

ABOUT THE STARS

HE young astronomer in Two on a Tower-that bitter-sweet story in which our great novelist Hardy tells of the weird fascination with which the study of the stars appeals to a sensitive nature, exclaims: "The imaginary picture of the sky as the concavity of a dome whose base extends from horizon to horizon of our earth, is grand, simply grand, and I wish I had never got beyond looking at it in that way. But the actual sky is a horror." "There is," he continues, "a size at which dignity begins; further on there is a size at which grandeur begins; further on there is a size at which solemnity begins; further on a size at which awfulness begins; further on a size at which ghastliness begins. That size faintly approaches the size of the stellar universe." "If you are cheerful and wish to remain so," he concludes, "leave the study of astronomy alone. Of all the sciences, it alone deserves the character of the terrible. If, on the other hand, you are restless and anxious about the future, study astronomy at once-your troubles will be reduced amazingly. But your study will reduce them in a singular way, by reducing the importance of everything, so that the science is still terrible, even as a panacea." The facts revealed by the study of astronomy which have this feature of ghastliness and terror relate to the enormous distances in space at which the stars are placed, and to their enormous number.

One may sometimes see on the coast or in some marshland a "pile-driver" at work. At a quarter of a mile distance you can see the great weight hoisted up by cranks and chains above the "pile," which stands upright but not yet driven very far into the ground. You see the weight let go; it drops vertically on to the pile, and you watch it rising some two or three feet on its return journey upwards, when suddenly you hear the sound of a sharp blow, and only after an effort realise that the sound was made more than a second ago, and that the workmen have had time to raise the weight 3 ft. before the sound travelled to you. Sound travels less than a quarter of a mile in a second. Light also takes time to travel, but it advances ever so much more quickly than sound, namely, 186,000 miles (and a bit more) in a second. It is, therefore, easy to calculate the number of miles traversed by light in a minute or in a year. There are thirty million seconds in a year. The light of the sun takes eight minutes to reach the earth, so, instead of stating the number of miles of this distance, we may say that the sun is eight "light-minutes" distant from the earth (about 89,000,000 miles). This is an enormous figure. The sun and his planets may be represented proportionately by a golden ball a foot in diameter, and a number of little spheres varying in size from that of a dried pea to a boy's marble, placed at distances from the golden ball varying from 50 ft. to 200 ft. Such a model is shown in the Museum of Practical Geology in Jermyn Street, London. Minute and scattered far apart as the planets of the solar system appear when thus represented, yet the solar system is a compact little group when we come to consider the distance from it of the other sunsthe "fixed stars," which exist literally in millions beyond it. The nearest of these stars (its name is Alpha Centauri) is no less than three light-years distant from us. A light

year is five and a half billion (that is, five and a half million million) miles. The nearest sun to us after our own sun is, therefore, about sixteen billion miles away and if its light were suddenly extinguished, we should not know of its extinction for three years.

How many-we may well ask-how many of these fixed stars-suns like our own-are there? Roughly speaking, we can see with the naked eye, reckoning both the northern hemisphere and the southern together (for the stars seen from the former are other than those seen from the latter), about 8000. Not many after all, one is inclined to say. But stop a minute and hear what the telescope reveals. With the best telescope about one hundred million can be seen, less and less brilliant and more difficult to see in proportion to their remoteness. And now we go further even than that. For within the last thirty years the great science of astronomy has been rejuvenated by the application of photography to its task. The invention of the "dry" plate, a sensitive photographic plate which does not spoil by prolonged exposure as the "wet" plate does, enables the astronomer to keep his telescope fixed by slow-moving clockwork on to a given region of the sky for four or five hours or more, and the very faint stars, invisible by the aid of the most powerful telescope-stars the light from which is so feeble that it could not affect the plate in a few seconds or minutes, have time by the continued action of their faint light to print themselves on the plate and sign, as it were, a definite record of their existence for man to see and measure, though they are themselves for ever invisible to his eye. It is not possible to say how many may be recorded in this way by photography; it depends on length of exposure. But some thousands of millions of stars can certainly be so recorded. These "unnumbered hosts" are of various degrees of brightness, and by

methods which astronomers have invented, but cannot be described here, it is actually known how they differ in size from one another (many are far bigger than our sun), and with some approach to certainty, how far off they are. Stars of four, five, ten, and more "light-years" away from us are well known. Astronomers actually estimate the decreasing abundance in space of stars as one passes from a sphere or spatial envelope of fifty light-years' distance to one of 250 light-years. Finally, reasons have been given of late for considering many of the "photographic" stars to be at a distance of 32,000 light-years. I will not produce the awful figure in miles, but the reader can refer back to the number of billion miles in a light-year! And what is beyond that? No one has seen, nor can any one guess. We cannot imagine a limit to space; neither can we imagine unending space dotted with an infinity of suns!

It is a legitimate and, indeed, a necessary inference, from what we know of these millions of suns-intensely hot, light-giving spheres-that they, too, like our own sun, are accompanied by much smaller bodies, planets which circle round them, as our sun's planets circle round him. Those planets have cooled down, as have those of the solar system, and so do not give out light. In any case, they are too small to be seen at so vast a distance. It is, on the whole, probable that the changes on someindeed, many of these planets have led to the production of living material similar to, but not necessarily identical with, that on this earth. It is, on the whole, more likely than not that there are intelligent beings existing on the planets of thousands of suns invisible to our eyes: suns revealed only by the print on a photographic plate of their light, which has taken thousands of years to travel from the regions of unseen obscurity to us. To have arrived by sober observation and reasoning at this con