40 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '] \ 



difference in level in cm. A comparison showed that the densities 

 used in the present calculations beyond 125,000 ft. were from three 

 to twentyfold larger than those derived from Wegener's data, so 

 that the values used in the present case were doubtless perfectly safe. 

 Densities beyond 700,000 ft. within the geocoronium sphere, must 

 be negligible, for not only is the density very small but the resistance 

 to motion is very small — due, according to Wegener, to the prop- 

 erties of geocoronium — a conclusion which is supported by the fact 

 that meteors remain, for the most part, invisible above this level. 



DIVISION OF THE ALTITUDE INTO INTERVALS 

 In dividing the altitude into intervals the only condition that must 

 be fulfilled is that the densities in any interval shall not dift'er widely 

 from the mean value in the interval. The least number of intervals 

 which satisfy this condition are given in the following table : 



Table IV 



The mean densities in intervals s^ to Sg, inclusive, were obtained 

 from figure 21, on which these intervals are marked. The remaining 

 densities were estimated as already explained. 



CALCULATION OF MINIMUM MASS FOR EACH INTERVAL 



The tables V and VI are calculated for a start, respectively, from 

 sea-level and from an altitude 15,000 ft. — i. c, the beginning of S3. 

 The procedure in each case is, however, identical. 



The process of calculation is as follows : At the beginning of any 

 interval we have the velocity already acquired during the previous 

 intervals, let us say Vq. This velocity is, of course, zero at the 

 beginning of the first interval. Assume any final velocity at random, 

 \\. for the interval in question. 



