326 ANNUAL OF SCIENTIFIC DISCOVERY. 



the border, another will do the same. The author thinks, moreover," 

 that he has noticed a connection between this behavior of sun-spots 

 and the configuration of the nearer planets, Mercury and Venus, and 

 it would seeni to be of this nature : Remembering that all motions are 

 from left to right, let us suppose that Mercury and Venus are both in 

 a line considerably to the left of the Earth ; then spots will decrease as 

 they come round from the left-hand side, and before they reach the 

 centre of the disk. On the other hand, if these two planets are con- 

 siderably to the right of the Earth, there will be a tendency for spots 

 to form on the right half of the disk, and to increase up to the border. 

 The author would, however, guard himself against the supposition that 

 he attributes all the phenomena of spots to the agency of these two 

 planets. 



RESEARCHES ON THE PLANET MARS. 



Mars, though not absolutely the nearest of our planetary neighbors, 

 is certainly of course, excluding the Moon, which is in many re- 

 spects a world far more different in physical condition from the Earth 

 than the proper planets more within our range of observation than 

 any other attendant of the sun. Venus, the next of the planets to the 

 Earth going sunwards, is often nearer to the Earth than Mars, whose 

 orbit envelops our own, can ever be ; but the difficulty of observing 

 a planet which is so bright that all the imperfections of our instruments 

 are exaggerated, and which, when at its nearest point to us, must usually 

 be observed at a low altitude, are so great, that we know less about 

 Venus than about almost any other of the planets except Mercury. 

 Mars, which can be observed, and has quite recently been closely ob- 

 served by Mr. Lockyer, of England, within the very moderate distance 

 of about fifty millions of miles, is at present the only planet into the 

 secrets of whose physical, as distinguished from purely mechanical, 

 structure we can at present hope to peep. We know all about it that 

 we know of any other planet, and a good deal more as well. We 

 know that the day and night of all the four planets, Mercury, Venus, 

 Earth, and Mars, are nearly of equal length, and considerably more 

 than double the days and nights of the more distant and more elabo- 

 rately moonlit (or ringlit) planets. We know that they are, all four, 

 much heavier, bulk for bulk, than the bigger planets, the little Mer- 

 cury being much the heaviest in material of the four ; we know that 

 they all have atmospheres of greater or less density ; and we know 

 very.little more about any of them except Mars. But of Mars the ob- 

 servations of Messrs. Beer and Madler, in 1830, 1837, and 1841, had 

 already given us a good deal of fresh knowledge, which Mr. Lockyer's 

 drawings, from observations made during the autumn of 1862, have 

 partly confirmed and partly supplemented. A recent astronomer has 

 asserted that " water would not remain fluid even at the Martial equa- 

 tor, and alcohol would freeze at the temperate zones." Probably no 

 assertion was ever less well grounded. The calculation is made on the 

 principle that Mars is so much farther from the sun that the intensity 

 of his rays is there only four-ninths of their intensity here. That is 

 true. But then so much more depends on the collecting effect of a 

 thick atmosphere than on the mere intensity of the sun's rays, that 

 water will freeze on Mont Blanc, where the mere rays are certainly 



