142 ANNUAL OF SCIENTIFIC DISCOVERY. 







However it may be, this ranch is certain, this phenomenon is caused 

 by matter which moves according to the same laws as the planets round 

 the sun, and it consequently follows that the whole mass which origi- 

 nates the zodiacal light is continually approaching the sun and falling 

 into it. 



This lio-lit does not surround the sun uniformly on all sides ; that 



*D " 



is to say, it has not the form of a sphere, but that of a thin convex 

 lens, the greater diameter of which is in the plane of the solar equator, 

 and accordingly it has to an observer on our globe a pyramidal form. 

 Such lenticular distribution of the masses in the universe is repeated in a 

 remarkable manner in the disposition of the planets and the fixed stars. 



From the great number of conietary masses and asteroids and the 

 zodiacal light on the one hand, and the existence of a resisting ether 

 on the other, it necessarily follows that ponderable matter must con- 

 tinually be arriving on the solar surface. The effect produced by 

 these masses evidently depends on their final velocity ; and, in order 

 to determine the latter, we shall discuss some of the elements of the 

 theory of gravitation. 



The final velocity of a weight attracted by, and moving toward, a 

 celestial body will become greater as the Light through which the 

 weight falls increases. This velocity, however, if it be only produced 

 by the fall, cannot exceed a certain magnitude ; it has a maximum, 

 the value of which depends on the volume ancX mass of the attracting 

 celestial body. The author then by a series of calculations, shows, 

 that an asteroid falling into the sun, would on arriving have a mo- 

 tion at least as great as that of a weight falling freely to the sun from 

 a distance great as that of the solar radius, or 90,000 geographical 

 miles ; and that the calorific effect of the percussion would equal to 

 from 27k to 55,000,000 of degrees of heat. 



An asteroid, therefore, by its fail into the sun, develops from 4,600 

 to 9,200 times as much heat as would be generated by the combustion 

 of an equal mass of coal. 



[ Throughout this memoir the degrees of heat are expressed in the 

 Centigrade scale. Unless stated to the contrary, the measures of 

 length are given in geographical miles. A geographical mile -g 1 ^ of 

 degree of latitude 1,878 meters, and an English mile 1*009 meters.] 



The Heat of the Sun. The question why the planets move in curved 

 orbits, one of the grandest of problems, was solved by Newton in 

 consequence, it is believed, of his reflecting on the fall of an apple. 

 This story i:i not improbable, for we are on the right track for the dis- 

 covery of truth when once we clearly recognize that, between great 

 and small, r.o qualitative but only a quantitative difference exists, 

 when we nvist the suggestions of an ever active imagination, and 

 look for the same laws in the greatest as well as in the smallest pro- 

 cesses of n iturc. This universal range is the essence of a law of 

 nature, and the touchstone of the correctness of human theories. 

 We observe the fall of an apple and investigate the law which gov- 

 erns this phenomenon ; for the earth we substitute the sun, and for 

 the apple a planet, and thus possess ourselves of the key to the me- 

 chanics of the heavens. 



As the same laws prevail in the greater as well as in the smaller 

 processes cf nature, Newton's method may be used in solving the 



