proceedings: philosophical society 353 



feet, on the "polarization" of increasing the thickness of the porcelain 

 plates, also whether a saturation test could not be utilized to determine 

 the possible functioning of electrons. 



In reply, Mr. SilsbeE stated that platinum electrodes had also been 

 used but with similar results; that no experiments had been made to 

 test the effect of increasing the thickness of the porcelain plates; and 

 that he did not think the saturation test could be made owing to the 

 introduction of thermal complications due to actual heating of the por- 

 celain, by the currents even before the currents ceased to be proportional 

 to the applied potential-differences. 



Mr. SoSMAN suggested the possibility of finding a solution of the 

 problem in a study of the glass in the porcelain. The paper was also 

 discussed by Messrs. Williamson and Bichowsky. Mr. Agnew com- 

 mented on the great variety of causes given for the failure of airplane 

 engines, and the frequent lack of consistency between explanation and 

 evidence. 



The 817th meeting was held at the Cosmos Club, March 29, 191 9; 

 President Humphreys in the chair ; 80 persons present. Minutes of the 

 815th and 8 1 6th meetings were read in abstract and approved. 



The first paper was persented by Mr. W. R. Gregg on Trans -Atlantic 

 flight from the meteorologist's point of view, and was illustrated by lantern 

 slides. 



Abstract Inasmuch as weather conditions constitute a vital factor 

 in the success or failure of trans-Atlantic flight, it is essential that these 

 conditions be known as accurately as possible, in order that an aviator 

 may know beforehand his "margin of safety" and may make his plans 

 accordingly. The purpose of the paper is, therefore, briefly to present 

 (i) a statement giving the present state of our knowledge relative to 

 average surface meteorological conditions over the portions of the 

 North Atlantic between Newfoundland and Ireland and between 

 Newfoundland and Portugal via the Azores; (2) a similar statement 

 as to free air conditions, particularly at altitudes of 500 to 1000 meters; 

 and (3) an analysis showing the assistance that may be rendered by 

 the winds, providing an aviator, with this in mind, carefully selects 

 his time for flight. 



Under the first and second headings conditions of temperature, 

 humidity, cloudiness, precipitation, fog, pressure and winds are briefly 

 summarized, this summary being based upon such few observations as 

 have been made at sea and to a greater extent upon those made over 

 adjacent land areas. In the application of the latter due consideration 

 has been given to the essential differences between marine and con- 

 tinental climates, particularly with reference to free air conditions. 



In the third part of the paper the necessity of having observations 

 at the time of flight is pointed out. If such observations are available 

 and if the airspeed of the machine is known, the meteorologist is able 

 quickly to indicate the successive directions toward which the airplane 

 should be headed, in order that it may keep to any desired course; 



