proceedings: philosophical society 335 



The paper was discussed at some length by Mr. Woodward, particularly 

 as regards the surface of reference, and by Messrs. Bowie, Gray, and 

 Buckingham. 



Mr. Bow^iE made a brief informal communication showing evidence 

 of nearly perfect isostasy in India from reductions at 14 gravity stations. 



The usual hour of adjournment being at hand, it was moved and carried 

 to extend the time to permit the reading of the second paper of the 

 evening by Mr. W. J. Humphreys On thunder storms. The author 

 discussed the mechanism of storms and applied in this connection the 

 conclusion from W. Simpson's work in India that electricity with rain is 

 essentially positive. The paper was illustrated by lantern slides showing, 

 among other things, in particular the barometric conchtions accompany- 

 ing different types of storms. At 10 :50 p.m. the meeting adjourned. 



The 741st meeting was held on May 9, 1914, at the Cosmos Club, 

 President Fischer in the chair; 30 persons present. 



Mr. L. W. Austin spoke on Recent experiments in the reception of radio- 

 telegraphic signals. The greatest obstacle not 3^et overcome in wireless 

 signaling is the presence of atmospheric disturbances which confuse and 

 often drown out signals being received; this difficulty is becoming greater 

 as the receiving apparatus is becoming more sensitive. The author 

 described methods to do away with this disturbance and in particular 

 recent experiments Avith tuning spark apparatus. The most recent and 

 interesting development is the improved oscillating audion and am- 

 pliphone of De Forest. The paper was discussed by Messrs. White, 

 Bowie, Bauer, Humphreys, Marvin and Bellinger as to automatic 

 receiving apparatus, greater facility of transmission for north-south than 

 east-west direction, latest ideas of causes of atmospheric chsturbances, 

 height of path, and amount of energy expended in sending, compared 

 with amount received. Mr. Austin stated there seemed to be no certain 

 e\'idence as to greater ease of transmission in any particular direction; 

 the disturbances are of local type and those at a distance, as discharges 

 between clouds ; there has been no close connection noted between weather 

 and receiving conditions. 



Mr. R. A. Harris then spoke On periodic quantities, especially motions. 

 This communication was concerned with a series or aggregation of 

 periodic terms, or with several such series considered simultaneously. 

 A term of the form 06*'^"* + "^ is regarded as representing the simplest 

 kind of periodic function because as t increases uniformly the function of 

 t represented will describe a circle about its origin at a uniform rate. 

 When there are several such terms, additional concepts arise, as ampli- 

 tude ratios, speed differences, relative phases, and quantities in which 

 these concepts are involved. A series of terms having the imaginary 

 exponential form represents epicyclic motion. The simultaneous use 

 of two series of terms where both commensurable and incommensurable 

 speeds occur is exemplified in the new tide-predicting machine. Three 

 series of periodic terms are suitable for space in general. At 10:10 p.m. 

 the meeting adjourned. 



