376 ANNUAL OF SCIENTIFIC DISCOVERY. 



towards it ; and this is a test which, perhaps, can be accurately applied in 

 this situation, by carefully delineating the shadows which fall in morning and 

 evening from the lofty walls of the crater. 



Mr. Nasmith, on the question of ancient traces of water in the moon, main- 

 tained the negative, and expressed his conviction that all the appearances 

 sometimes relied on for the affirmative were explicable by considerations of 

 the peculiar character of the old volcanic operations on the moon. 



SOLAR SPOTS. 



The following is an abstract of a paper communicated to the American 

 Association on the above subject, by Dr. Peters, of Denmark: 



His conclusions, he said, were drawn from observations made in Naples, in 

 the year 1845-6. He and his collaborateurs had computed eight hundred 

 and thirteen heliographic places of two hundred and eighty-six spots. They 

 had ascertained that the spots were not invariably attached to the sun's sur- 

 face, but that they had motions of their own. These motions were a general 

 tendency to move towards the equator, and where a new spot broke out in 

 the neighborhood of another, the old one moved away from it as if it were 

 pushed away. New spots generally broke out to the east of old ones, and 

 had a motion towards the west, and the motions in longitude were far more 

 considerable than those in latitude. These motions were in some instances at 

 the rate of three or four hundred miles in an hour. Two zones of the sun's 

 surface were particularly fruitful in spots; the maximums occurring at the 

 parallels of 21 degrees of north latitude, and 17 degrees of south. Instances 

 had been noticed in which spots reappeared after an interval of two or three 

 hundred days, although there was one difficulty in determining this accurately 

 arising from the uncertainty of the time of rotation. Since spots arose from 

 invisible points at the exact moment of their origin, they could not be 

 studied. 



The first indication which the telescope revealed was a sort of bubbling 

 agitation in the luminous layer. To this succeeded a small spot, which 

 rapidly attained its full size almost always in the course of a day. They 

 remained in this, the vigorous epoch of their life, with a well defined penum- 

 bra of regular and rather simple shape, for ten, twenty and sometimes even 

 for fifty days. But at last their time came. Their margin had always been 

 slightly notched, and soon the notches grew ominously large and deep, pene- 

 trating far into the mystic realm of darkness, while hostile columns of light 

 arose as if by magic, occupying the centre. Deeper and deeper grew the 

 invading notches, until, at last, electric flashes passed between two of the more 

 prominent, across the disc. The victory was gained, the centre pierced, and 

 the spot divided into two, after which it was very easy to cut it up in detail. 

 Dr. Peters explained these facts, by the assumption of volcanoes sending up 

 gaseous matter which parts the luminous covering. All the world knows that 

 the sun is supposed to have, at least, two atmospheres, the one next its sur- 

 face dark but supporting another which is luminous, and which sends forth 

 the light and heat which we find so very convenient. 



