METEORS AND AEROLITES. 289 



yet cognizance. But we have no right to carry hypothesis 

 farther, on a point to which even the ability of Poisson has 

 been directed without any determinate conclusion. 



Considering that all meteors involve the presence of 

 matter in some form, and that aerolites show it by pre- 

 cipitation of solid masses on the earth, it is a question of 

 interest what happens in the cases where we have not this 

 direct result. The answer can hardly go beyond conjecture. 

 Many meteors, even those containing solid matter, may be 

 deflected in such degree towards the earth as to become 

 luminous in a part of their course, yet still preserve their 

 own independent orbits. Others, again, may undergo ex- 

 plosion or disruption during this contiguity, and throw down 

 the same matters as those contained in meteoric stones, but 

 under the form of powder or dust. Though this result is 

 obviously more difficult of discovery, yet we have numerous 

 proofs of the fact in the records of every age. Then, 

 further, it is to be remembered how very small a proportion 

 of the aerolites falling can come within human observation. 

 The chances against any one stone being seen to fall on the 

 earth are so numerous as to be hardly calculable, the mere 

 interposition of night in our record of time entering largely 

 into this question. The sight of such an event in fact is the 

 exception, and not the rule. Weighing all this rightly, and 

 taking into account also that the Ocean covers about three- 

 fourths of the globe, and that a large proportion of its land- 

 surface is either unknown or uninhabited, we shall not be 

 greatly surprised at the estimate of Schreibers that upwards 

 of 700 meteoric stones, of various size, must fall annually 

 upon the surface of our planet. It is only in the present 

 state of science, when the most minute quantities are sub- 

 jected to notice and calculation, that we could allude without 

 ridicule to the fact of the increment thus made, and con- 

 tinually making, in the amount of solid matter of the globe. 



