MERRILL] METEOR CRATER OE CANYON DIABLO, ARIZONA 493 



These illustrations are sufficient to show the contradictory nature 

 of the evidence. Such contradictions can be partially explained by 

 taking into consideration the varying angles at which the meteorites 

 come in contact with the earth and the direction of their flight. One 

 falling from a great height almost vertically would naturally have 

 a greater power of penetration than one coming at a low angle. 

 More important yet is the direction of flight of the meteor with 

 reference to the earth. If following the earth in its course about 

 the sun, the apparent speed would be but differential. Thus a mete- 

 orite with a velocity of 25 miles per second overtaking the earth 

 traveling at the rate of 19 miles per second would enter our atmos- 

 phere with an initial speed of but 6 miles per second, and this through 

 atmospheric friction would be so far reduced as to give the lower 

 figures above mentioned, or the speed of an ordinary falling body. 

 In the case of a meteorite pursuing a retrograde course, conditions 

 are greatly exaggerated. With a velocity of 25 miles a second, it 

 meets the earth traveling in the opposite direction at the rate of 19 

 miles per second, and hence enters our atmosphere with an initial 

 velocity of 44 miles per second. Here, as before, the retarding effect 

 of the earth's air cushion must be considered. With such a velocity, 

 friction must be tremendous, and even in the few seconds occupied 

 in its transit large quantities of its material must be dissipated. That 

 such is the case we have unquestionable proof in the luminous trains 

 of meteors, and H. E. Wimperis 1 has calculated that "no iron meteor 

 the original weight of which was less than 10 to 20 pounds reaches 

 the earth's surface," being entirely consumed in its passage. 



Schiaparelli, as quoted by Fletcher, 2 has shown that if a ball 8 

 inches in diameter and of 32^ pounds in weight enters our atmo- 

 sphere with a velocity of 44^ miles per second, its velocity on ar- 

 riving at a point where the barometric pressure is still but 1/760 

 of that at the earth's surface will have been already reduced to y/ 2 

 miles a second — figures which correspond fairly well with the esti- 

 mates made on the flight of the Weston and Guernsey stones. 



Dr. R. S. Woodward, as quoted by Mr. Gilbert, 3 has calculated 

 that a body reaching the surface of the moon with a velocity of 1^2 



1 Nature, vol. 71, 1904-05, p. 82. The writer well remarks : "I am aware 

 that the whole structure of the investigation (i. e., his calculations) rests on 

 the evil principle of extrapolation, but until man is capable of experimenting 

 with velocities of 10 or 20 miles per second, and surviving thereafter to record 

 his results, no other manner of investigation seems possible." 



2 Introduction to the Study of Meteorites, 1896, p. 26. 



3 The Moon's Face, Bull. Philosophical Soc. of Washington, vol. xil, 1893, 

 p. 258. 



