CONTENTS XXV 



Electron Emission 



667. Electron emission from hot solid elementary substances 547 



668. " " " monomolecular thorium-coated filaments . 547 



669. Emission current, efficiency, diffusion, Th on W 547 



670. Electron emission from other coated filaments 548 



671. Photoelectric effect 54-8 



672. Contact (Volta) potentials 548 



673. Electron affinity of the elements, in volts 549 



674. Molecular velocities 55° 



675. " free paths, collision frequencies, and diameters .... 550 



676. Cross-sections and lengths of some organic molecules 551 



677. Size of diffracting units in crystals 551 



678. Ionic mobilities 55 2 



679. Diffusion coefficients 55 2 



680. Colloids, general properties of 553 



681. " molecular weights of 553 



682. " : Brownian movement 553 



683. " Adsorption of gas by finely divided particles 554 



684. Heats of adsorption 554 



685. " Molecular heats of adsorption and liquefaction (Favre) . 554 



Meteorology 



686. Transmission of solar radiation by earth's atmosphere 555 



687. Ultra-violet solar radiation at earth's surface 555 



688. Relative intensity of solar radiation 556 



689. Mean monthly and yearly temperatures 556 



690. Temperature variation over earth's surface (Hann) 557 



691. " " with depth (land and ocean) 557 



692. Atmosphere : Miscellaneous data. Variation with latitude .... 558 



693. " Var. percentage composition with altitude (Hum- 

 phreys) 558 



694. Atmosphere: Var. temp., pressure, density with altitude (Hum- 



phreys) 558 



695. Atmosphere: Standard [Nat. Adv. Com. Aeronautics] 559 



696. " p. in dynes/cm 2 , summer and winter, day and night 

 (Maris) 560 



697. Atmosphere: Molecular densities of atmospheric gases (Maris) . 560 



698. " Geopotential, dynamic heights 561 



699. " Equivalents, in geodynamic km, of geometric heights. 561 



700. " " " geometric " " dynamic 561 



701. " Temperature variation lower 25 km with lat. and alt. 562 



702. Seasonal variation of tropopause at Agra and Batavia. 562 



