the Origin of Meteoric Stones. 341 



meteoric stones after they are formed in the atmosphere. Neithe 

 are we acquainted with any power which could give such a hori- 

 zontal velocity to the different materials while in their diffused 

 state, or while held in solution by some gaseous fluid. Electric 

 attraction might indeed give a slow motion to themj but it is 

 quite incapable of giving such a velocity as to account for the 

 phsenomenon in question; it may perhaps, in very favourable cir- 

 cumstancesjbe able to produce a Iiorizontal velocity of about thirty 

 or forty feet per second ; but this is very far short of what meteoric 

 stones must have at the moment they are formed. Tlie only power 

 in nature, with which we are at present acquainted, besides elec- 

 tricity, that appears to be able to give any considerable horizontal 

 velocity to a solid mass formed in the atmosphere, is the expan- 

 sive force of inflammable gases when exploded. We know that the 

 rapidity with which several mixtures of this kind expand at the 

 moment of explosion is very great ; some of them probably at the 

 rate of several thousand feet per second. Let us therefore inquire 

 whether this can be the source of tlie horizontal motion of me- 

 teoric stones. 



It is well known that some of these stones have fallen so ob- 

 liquely, and with such force, that their horizontal velocity could 

 not be less than 200 feet per second, when they struck the ground. 

 But it is evident that the original horizontal velocity of any me- 

 teoric stone must be very much reduced by the resistance of the 

 air before it reaches the earth : thus, for example, if we suppose 

 a stone to be spherical, to weigh lOOlbs. and to have been formed 

 at the height of four miles; it will be found by calculation that 

 it would require to be projected with a velocity of considerably 

 more than 2000 feet per second, that its horizontal velocity when 

 it reached the ground might be 200 feet per second. Again: air 

 at the height of four miles is about 1870 times lighter than water, 

 and the stone being 31 times heavier, it follows that the stone 

 must be above 6500 times the weight of an equal bulk of air at 

 that elevation. Now every meteoric stone must be formed very 

 near to that point which is acted on equally in all directions, by the 

 expansive force produced by the explosion : and when we consi- 

 der that the horizontal velocity can only arise from the excess of 

 the force applied on one side over that which is applied on the 

 others, how enormously great indeed must the rapidity be, with 

 which this elastic gas or vapour expands itself, if only a small por- 

 tion of its force can comnumciate a velocity of more than 2000 

 feet per second, to a body 6500 times as dense as itself, and that 

 too in a situation completely unconfincd ! It will not be sufficient 

 that it expand itself with a velocity of 7 or 8000 feet per second; 

 no, not even fifty times 7000 would be enough. Hence it ap- 



Y 3 pears. 



