94 AUSTIN: HIGH FREQUENCY RESISTANCES 



is an abrupt change in the temperature gradient. At first it is 

 rather under 5°C. per kilometer, and then as the elevation still 

 further increases and the temperature steadily grows colder, so 

 that less and less moisture condenses out per degree change, it 

 grows greater, with, of course, the adiabatic gradient for dry air, 

 or 10°C. per kilometer, as the limit towards which it approaches. 



Now the ordinary summer temperature gradient in the free 

 atmosphere, between the elevations of 1.5 and 8 kilometers, is 

 approximately G'^C. Hence, in the assumed case, the tempera- 

 ture within the rising column will begin to increase above that of 

 the surrounding atmosphere at the same level, as soon as conden- 

 sation begins, and the temperature difference, together with the 

 resulting buoyancy, will go on increasing with the elevation to a 

 certain maximum and then decrease to a zero difference. In 

 fact the inertia of the rising' mass will carry it beyond the equilib- 

 rium level to heights where it will be colder and denser than the 

 adjacent air, and from which it therefore must correspondingly 

 fall back until final equilibrium of temperature and density are 

 established. 



Seemingly then the real cause of the violent uprush within 

 large cumulus clouds is the difference in temperature between the 

 interior of the clouds themselves and the surrounding atmosphere 

 at the same level, due, as explained, to the change in the tempera- 

 ture gradient caused by the latent heat of condensation. 



PHYSICS. — The high frequency resistances of inductances. 

 L. W. Austin, U. S. Naval Radio-telegraphic Laboratory. 

 To appear in full in the Bulletin of the Bureau of Standards. 



TVTiile the high frequency resistance of non-inductive resist- 

 ances can be easily determined by substitution methods, the 

 determination of high frequency resistance of inductances offers 

 great difficulties. The decrement and half deflection methods, ^ 

 in addition to being difficult to apply when very accurate results 

 are desired, have also the disadvantage of including in the ob- 

 served resistance all the sources of energy loss in the circuit. 

 The present method, while laborious, seems capable of giving 

 much more exact results than the others mentioned. 



1 Bulletin Bureau of Standards, 9: 66. 1912. 



