Mr. R. P. Greg on the Lunar Origin of Aerolites. 435 



laws of chance, that these bodies should have been passing 

 through an atmosphere for ages and none have yet encountered 

 the body of the earth." 



It is not strictly true that no meteorite is known of any great 

 size, i. e. not larger than the well-known cannon-balls of granite 

 at the Dardanelles, for one or two of the larger meteoric iron 

 masses have been described by travellers as being 7 feet in 

 length and weighing 15 tons. It would be improbable that 

 such a mass could be projected beyond the mouth of either a 

 lunar or terrestrial volcano, much less reach a height of several 

 thousand feet. 



The following calculations will show that a mass of iron 

 havmg a spherical form, and weighing 20,000 lbs., could not 

 reasonably have a greater velocity than 372 feet in a second if 

 projected from a lunar volcano. The calculations are based on 

 the following premises. 



A stone having 5-6 inches in diameter, with a density of 3'0, 

 and weighing 10 lbs., is assumed to be projected from a lunar 

 volcano at the rate of 9000 feet in a second, i. e. with a velocity 

 more than sufficient, according to Dr. Smith and others, to allow 

 It to pass the limits of mutual attraction between the moon and 

 the earth. 



Taking the sp. gr. of iron 8-0, and bearing in mind that the 

 areas are as the squares and the masses as the cubes of the dia- 

 meters, we arrive at the following results. A mass of iron ('^lo- 

 bular) to weigh 20,000 lbs., sp. gr. 8, will be a little over o'o-g 

 mches in diameter ; found thus : — 



a/ /20,000 lbs X 16 oz. X 1728\ 



^( 8000sp.gr.x-523 H= ^132009 = 50-9 in. nearly. 



A similar mass of stone to be the same weight, and sp, gr. 3-0, 

 must be 70-6 inches in diameter; found thus : — 



Now if a piece of stone 5*6 inches in diameter, weighing 10 lbs., 

 be projected with a velocity of 9000 feet per second, a mass 

 70-0 inches diameter, and weighing 20,000 lbs., could only be 

 projected with a velocity of 715 feet per second,' because" the 

 weights would increase so much faster than the sectional area. 

 Lbs. Diain. Velocity. 



Thus as ?2^ . lif^l 



10 ■ (5-62)2 



9000; 



2000 : 1|^1J^ :: 900 : 715 feet. 



