AEROLITES. 137 



bodies. The idea is completely inadmissible that they are concretions formed within the 

 limits of the atmosphere. The ingredients that enter into their composition have never ! 

 been discovered in it, and the air has been analysed at the sea level and on the tops of 

 high mountains. Even supposing that to have been the case, the enormous volume of 

 atmospheric air so charged required to furnish the particles of a mass of several tons, not j 

 to say many masses, is, alone, sufficient to refute the notion. They cannot, either, be i 

 projectiles from terrestrial volcanoes, because coincident volcanic activity has not been 

 observed, and aerolites descend thousands of miles apart from the nearest volcano, and 

 their substances are discordant with any known volcanic product. Laplace suggested 

 their projection from lunar volcanoes. It has been calculated that a projectile leaving the 

 lunar surface, where there is no atmospheric resistance, with a velocity of 7771 feet in 

 the first second, would be carried beyond the point where the forces of the earth and 

 moon are equal, would be detached, therefore, from the satellite, and come so far within 

 the sphere of the earth's attraction as necessarily to fall to it. But the enormous number 

 of ignited bodies that have been visible, the shooting stars of all ages, and the periodical 

 meteoric showers that have astonished the moderns, render this hypothesis untenable, for 

 the moon, ere this, would have undergone such a waste as must have sensibly dimi- 

 nished her orb, and almost blotted her from the heavens. Olbers was one of the first to 

 prove the possibility of a projectile reaching us from the moon, but at the same time he 

 deemed the event highly improbable, regarding the satellite as a very peaceable neighbour, 

 not capable now of strong explosions from the want of water and an atmosphere. The 

 theory of Chladni will account generally for all the phenomena, be attended with the fewest 

 difficulties, and, with some modifications to meet circumstances not known in his day, it 

 is now widely embraced. He conceived the system to include an immense number of 

 small bodies, either the scattered fragments of a larger mass, or original accumulations of 

 matter, Avhich, circulating round the sun, encounter the earth in its orbit, and are drawn 

 towards it by attraction, become ignited upon entering the atmosphere, in consequence of 

 their velocity, and constitute the shooting stars, aerolites, and meteoric appearances that 

 are observed. Sir Humphry Davy, in a paper which contains his researches on flame, 

 strongly expresses an opinion that the meteorites are solid bodies moving in space, and 

 that the heat produced by the compression of the most rarefied air from the velocity of 

 their motion must be sufficient to ignite their mass so that they are fused on entering the 

 atmosphere. It is estimated that a body moving through our atmosphere with the velo- 

 city of one mile in a second, would extricate heat equal to 30,000 of Fahrenheit a 

 heat more intense than that of the fiercest artificial furnace that ever glowed. The chief 

 modification given to the Chladnian theory has arisen from the observed periodical occur- 

 rence of meteoric showers a brilliant and astonishing exhibition to some notices of 

 which we proceed. 



The writers of the middle ages report the occurrence of the stars falling from heaven 

 in resplendent showers among the physical appearances of their time. The experience of 

 modern days establishes the substantial truth of such relations, however once rejected as 

 the inventions of men delighting in the marvellous. Conde, in his history of the dominion 

 of the Arabs, states, referring to the month of October in the year 902 of our era, that on 

 the night of the death of King Ibrahim ben Ahmed, an infinite number of falling stars 

 were seen to spread themselves like rain over the heavens from right to left, and this year 

 was afterwards called the year of stars. In some Eastern annals of Cairo* it is related that 

 " In this year (1029 of our era) in the month Redjeb (August) many stars passed^ with a 

 great noise, and brilliant light ; H and in another place the same document states :-^-" In 

 the year 599, on Saturday night, in the last Moharrem (1202 of our era^ and on the 19th 

 of October), the stars appeared like waves upon the sky, towards the east and west ; they 



