28 Journal of the Mitchell Society [September 



one degrees. Readings were taken for every three inches of fill, the 

 material being shovelled in horizontal layers. 



The tabulated quantities of these experiments are defined as fol- 

 lows: 



]i = height of fill, feet; 



P = \/ H' + V*, total pressure per foot width ; 

 H =: horizontal component per foot width, pounds; 

 V =: vertical component per foot width, pounds ; 



$' == angle of inclination of the resultant from the normal to the back of 

 wall ; tan $' = V/H ; 



X ::z height of point of application above the base of the wall = — -— L^ — - — - 



H total 



x/h = ratio of height of the point of application of the resultant to total 



height of fill; 

 H* =: theoretical horizontal component from formula H =z 14 wh^tan^ (45° — 



V2 O) ; 



w = weight per cu. ft. of filling material; 



$, = angle of natural slope (40 deg., as determined for this material) ; 



Hj = same as H, where 



$2 := angle of internal friction (34 deg., as determined for this material). 



h F II V (J)' ^ _ H, Hj 



2 ft. 62 lbs. 54 lbs. 32 lbs. 30° 50' .425 44 lbs. 56 lbs. 

 4 242 205 131 32° 50' .358 174 226 



6 545 464 285 31° 30' .365 393 507 



Conclusions — For this case, horizontal fill and vertical Avail, the furnuila 

 II =io ^vh^tnn^ (45 — i^ ^) may safely be used, if (^ is t;ikou as tlie angle 

 of internal friction. For this special case, Coulomb's and Eankin'p theories gire 

 the same formula. 



Otto Stuiilman, Jr. — Theory of the Audion and its Application to 

 the Wireless Telephone. 



Through the courtesy of the American Telegraph and Telephone 

 Company three reels of moving pictures were shown, the first two 

 of which illustrated the theory of the audion and the third its ap- 

 plication to the wireless telephone. 



Preliminary experiments were shoAvn to illustrate a stream of elec- 

 trons and how this same stream of electrons functioned in the case 

 of the audion. The subsequent discussion went into details of the 

 origin of the discovery and development of the thermionic effect and 

 the contributions made by Richardson, his students, and the results 

 of recent experiments on the audion as developed by the research 

 laboratories of the great electrical manufactories of the country. 



