DISCUSSION OF MOTIONS OF METEORITES 



115 



section N M being equivalent to a minute wheel on wliich the top 

 rolls. This wheel, on account of the rapid rotation of the top, acts like 

 the driving wheels of a locomotive, propelling the top and accelerating 

 the precession, resulting therefore in a rise of the axis and the '' sleep " 

 of the top. Precisely similar conditions are present in the case of the 

 meteorite. In this case the " floor " on which the rotating body spins is 

 an elastic one, and consists of the dense air near the point D (figure 1), 

 at which the air pressure is a maximum. Therefore the meteorite no 

 sooner takes on its motion of precession than the rate is augmented by 

 the rolling of the meteorite on the cushion of dense air, resulting in 

 a "sleep ''of the meteorite. This explains why the body must pass 

 through the air with its flat face presented broadside to the resisting 

 medium. 



B 



Figure 5. — Diagrams illustrating Movements of Spinning Top. 



A = diagram illustrating the blutit point of a top spinning on the floor ; B = diagram illustrating 

 a top with hollowed apex spinning on a pointed standard. 



The curvature of the face of the meteorite would have important 

 effects on the position of the center of pressure. If the convex side 

 were the front or the side toward the earth, the effect of the curvature 

 would be to increase the distance of the center of pressure Cfrom the 

 middle point 0. If the concave side were in front, then the center of 

 pressure would be moved toward 0, and if the concavity were sufficient, 

 the center of pressure would pass to the other side of (9, and the meteor- 

 ite would be reversed, the convex side passing to the front. Hence 

 unless the curvature was ver}^ slight, the convex side would be the one 

 which would constitute the front side of the meteorite. Figure 5, B^ 



