NO. l6 METEOR-ORBITS IN THE SOLAR SYSTEM — VON NIESSL 29 



In both these tables the altitude 33 km., at which the planetary 

 velocity is almost completely neutralized, is almost exactly equal to 

 the average altitude of stoppage given for detonating meteors on 

 page 26. But the method of the diminution of the velocity is con- 

 trary to all other experiences. Thus, for instance, in the first table 

 the estimated duration for the reduction from 129 km. down to 

 33 km. velocity should be only 1/18 part of the entrance velocity 

 and for meteors that are first observed in lower regions, for instance 

 between 80 km. and 33 km. which frequently occurs the reduction 

 .should indeed amount to only 2/36. Practically for meteors that have 

 been observed only in the lowest part of the path, we obtain almost 

 always much lower velocities, but certainly not to the extent here 

 given. 



For an entrance velocity of 16 km. the observed average velocity 

 between 94 and 33 km. in altitude is only \ of the original, or still 

 too small to observe. Nothing important is changed with respect to 

 these data if we make still other assumptions than those of I and II. 



The true geocentric velocity of the Leonids among which there are 

 many particularly bright shooting-stars is given us with some cer- 

 tainty from the known orbital period and amounts to not much less 

 than 72 km. For a small body in this meteoric stream of 2 mm. 

 diameter and 0.12 gram weight, whose orbit intersects the atmosphere 

 at an inclination of 30 degrees to the horizon, we should have to 

 divide by 20 the atmospheric pressures above given under case I, 

 hence the appropriate altitudes will be as follows : 



