POPULAR ASTRONOMY.
Bide-lights on Astronomy. By Simon Newcomb. (Harper and Brothers. Ts. 6d. net.)—Professor Newcomb, who has so long steed at the official head of astronomy in the United States, is a most lucid and entertaining writer, and such, a book of essays and lectures on his own subject as he has now published is quite sure of a hearty welcome from those non-technical readers to whom it appeals. The interesting paper on "Making and rising a Telescope," for instance, in the course of its thirty pages tells the layman practically all that he wants to know about the way in which Galileo's optic tube has been developed into a splendid instrument for piercing the mysteries of space, and explains the mechanical difficulties which cease the preparation of a great modern telescope to be so lengthy and delicate an operation. The majority of Professor Newcomb's essaye deal rather with the speculative than the practical side of astronomy, and describe the latest views held on that fascinating problem of the structure, duration, and extent of the universe. In the first of them he sets forth "the unsolved problems of astronomy," such as that involved in "the greatest fad which modern science has brought to light,"—the fact, namely, that our whole solar system is on a journey towards the constellation Lyra, familiar to most of ne by reason o the brilliant bluish- White star Vega which marks its situation in the neighbourhood of the north celestial pole. Every year we are about three hundred million miles nearer to this star, and yet, since the dawn of humanity on the earth, no visible change has occurred in its brightness, so vast is the distance which separates us from it, One of the tussolved problems of astronomy is to decide whether this flight of the sun and its attendant planets is a true journey towards Vega, or whether it is merely part of an incredible vast orbit which we are describing about some other sun, still undis- tinguishable amidst the countless orbs which strew the night sky. Some of the'other suns, we know, are actually describing such orbits. Some of the stars, again, like the vast orb of Arcturus, are engaged on similar journeys with so huge a velocity that the whole stellar system, so far as we can measure it, is in- sufficient in mass to deflect their motion from a straight line, and we have to ask ourselves if these "runaway stars" are in truth visitants from some external universe, merely passing through our system in the lapse of uncounted ages. All these problems Professor Newcomb handles with great illuminative power; he is certainly a star of the filet magnitude in the astronomical world. —Natural Phenomena. By F. A. Black. (Gall and Inglis. 6$. net.)—Mr. Black's unpretentious book gives an intelligible and interesting account of some astronomical and terrestrial problems of daily interest. He explains why local time differs in various parts of the world, why the sun and moon look huger when they are near the horizon than when they are high up in the sky, how the weather is supposed to move in cycles, and so forth. All thoughtful readers will find his book very satisfactory, and will close it with the sense of knowing more about the mechanism of the world than when they took it up.
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