XXVI CONTENTS 



703. Atmosphere: Seasonal variation height of tropopause over Batavia. 562 



704. Atmospheric ozone 563 



705. Mean free path, air molecules 563 



Geodesy 



706. Acceleration of gravity : For sea-level and different altitudes . . . 564 



707. " , various world stations 565 



708. " " " (g) in the United States 566 



709. Some places of anomalous gravity 567 



710. Length of seconds pendulum at sea-level and for different latitudes. 568 



711. [Replaced by Table 716, which see] 568 



Geophysics 



712. Miscellaneous geographical data 569 



713. Densities and pressures of earth's interior 569 



714. Velocities of earthquake waves 569 



715. Elastic constants of earth's interior 569 



716. Miscellaneous geophysical data 570 



717. Age of earth and its strata 571 



718. (a) Geologic age determinations based on the lead method .... 571 

 (b) The age of the earth 571 



719. Geochemical data 572 



720. The earth's rotation : Its variation 573 



721. Tides, sea-level, level net 574 



Terrestrial Magnetism 



722. Magnetic and electric data for sun and earth 574 



723. Magnetic constants of the earth 575 



724. North magnetic pole 575 



725. South " " 575 



726. Chart : World isogonic lines, D 576 



J2.J. Chart : World isoclinic lines, / 576 



728. " isodynamic lines, H 577 



729. " " isoporic " D 577 



730. " " " U I 578 



731- " " " " H : 578 



732. Annual change in magnetic declination, D 579 



733. " " " inclination, / 579 



734. horizontal intensity, H 579 



735. Chart : World isoporic lines, vertical intensity 580 



736. " " " " total intensity 580 



737. Mean annual values of magnetic elements at observatories .... 581 



738. " " " " " " . bibliography 589 



739. Secular change in declination, United States [1820-1930] .... 590 



