6 THE HARMONIES OF NATURE. 



numbers. During nine hours of observation in Boston,, when 

 they were described as falling like snowflakes, 240,000 meteors 

 were calculated to have been observed. The number falling in 

 a year might perhaps be estimated at hundreds or thousands 

 of millions, and even these would constitute but a small portion 

 of the total crowd of asteroids that circulate round the sun. As 

 these bodies, while obeying the earth's attraction, traverse our 

 atmosphere with planetary velocity, they would no doubt cause 

 a terrible bombardment, and from their vast numbers render 

 our planet absolutely uninhabitable, if their very speed had not 

 been made the means of neutralising their otherwise disastrous 

 effects : for, raised to incandescence by the atmospheric friction 

 engendered by this enormous velocity of from eighteen to thirty- 

 six miles a second, by far the greater portion of the aerolithes are 

 dissipated by heat, and a small number only reaches the surface 

 of the earth under the solid form of meteoric stones. 



Interesting by their celestial origin, these masses are still 

 more so as the only tangible and ponderable proofs we possess 

 of the material existence of a world beyond our own as teaching 

 us that the substances of which our earth is composed exist 

 also beyond its limits : for the chemist finds the meteoric stones 

 composed of iron, nickel, cobalt, silica, aluminium, and other 

 terrestrial elements, nor do they contain a single atom of any 

 substance that is unknown to us on earth. This circumstance 

 sufficed to render it very probable that our whole solar system 

 has been constructed of identical materials ; but the wonderful 

 researches of Bunsen and Kirchhof have raised probability to 

 certainty, by proving that sodium, calcium, magnesium, chro- 

 mium, iron, and other metals are constituents of the solar at- 

 mosphere and of the sun's central orb.* 



However vast the scale of our planetary system, however inca- 

 pable our imagination may be to grasp its immensity, it still 

 forms but a minute portion even of the visible universe ; for 

 how insignificant in point of numbers, size, and distance are all 

 the satellites revolving round our sun, in comparison to the 

 countless hosts of the sidereal heavens ! So enormous are their 

 distances, that the immense diameter of the earth's orbit, as 



* The reader will find an excellent account of the experiments which led to this 

 brilliant discovery in Professor Tyndall's admirable Lectures on Heat, pp. 408-415. 



