1G20 Poteatiiil — Periodical Variations. 



1G30 Lig'litning and otliei" I)isciiar,ii,'es, 



1()40 Thunderstorms. 



IGoO Aurora. See al^o E 5400, (JOr.O. 



1660 Aurora peiiodiciiy. 



CLIMATOLOGY AND WEATHER. 



1700 General. 



1710 Agricultural. 



1720 Phenolog'ical. 



17o0 Hygienic. 



Weather Forecasting. 



1750 General. 



1700 Weather Prog-nostics. 



1770 Synoptical Charts. 



Meteorological Registers. 



1800 General. 



1810 Registers giving- Hourly Mean Values. 



1820 Registers — Daily Mean Values. 



18o0 VVeathei- lleports— Daily. 



1840 Weather Reports Un- Longer Pei'iods. 



1850 Meteorological Log'-bjoks. 



1860 Non-instrumental Records. 



1870 Meteoi'ological Charts. See also 1770. 



When necessary the topographical symbols used in the 

 (jeography schedule may be added to any of the numbers, and 

 used in conjunction witli them. 



TERRESTEIAL MAGNETISM. THE COMPASS. 

 EARTH CURRENTS. 



3000 General. 



oOlO Magnetic Observatories. Methods of Measuring- the 



Values and Variations of the Mag-netic Elements. 



See also C 5440. 

 3020 Mag-netic State of the Surface of the Earth. Surveys. 



Isomagnetics and (Gaussian Coefficients. 

 3030 Secular Changes. 



3040 Diurnal and otiier Periodic Magnetic Variations. 



3060 Mag-netic Storms, 



3060 Relations between Terrestrial Magnetism ;iiid the 



Heavenly Bodies. 

 3070 Relations between Terrestiial Mag-netism and Geology, 



Earth-Currents, etc. 

 3080 Theories of Terrestrial Magnetism. 



30U0 Theory of the Compass. Mag-netism of Ships. 



4100 Earth Currents. 



