Intelligence and Miscellaneous Articles. 753 



different bases. Four of the results lay between 4315-5 and 4310*6 

 metres, the other two being respectively 4309*0 and 4318*7. It 

 is suggested that theodolite observations taken — usually in the 

 afternoon— along a meridian may suffer from irregularity of 

 heating as between the east and west sides of the instrument, 

 and that this may account for a "twist" believed to exist in 

 the present case. 



(B) Astronomy. Determination of Time, Longitude, Latitude 



and Azimuth, 5th Edition. By William Bowie. Special 



Publication No. 14 (quarto pp. 177). Washington, 1913. 



This is a revised and enlarged edition of a manual issued by 



the U.S. Coast and Geodetic Survey to " serve as a guide to the 



observer in the held and the computer in the office in carrying on 



the astronomic work of the Survey." Except that it supposes the 



reader to refer to textbooks like Chauvenet's for the proofs of 



the formulae, it is practically a complete treatise on the astronomical 



side of survey work. There are 29 illustrations, showing various 



patterns of theodolites and their mountings, chronographs, signals 



and signal lamps, observing tents and marks of various kinds. 



The methods of observation and reduction are explained in detail 



with illustrations, and there are a number of useful tables. 



LXXXVII. Intelligence and Miscellaneous Articles. 



BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 

 COMMITTEE FOR RADIOTELEGRAPHIC INVESTIGATION. 



Special Investigation. 



Effect on the Propagation of Electric Waves of the Total Eclipse 



of the San, 2lst August, 1914. 



r pHE forthcoming total eclipse of the sun affords an exceptional 

 -*- and important opportunity of adding to existing knowledge of 

 the propagation of electric waves though air in sunlight and 

 in darkness, and across the boundaries of illuminated and unillu- 

 miuated regions. The eclipse will be total along a strip extending 

 from Greenland across Norway, Sweden, Eussia and Persia to the 

 mouths of the Indus. In Eussia the duration of totality will be 

 a little more than two minutes. 



There are two main points calling for investigation during the 

 eclipse. In the first place, the propagation of signal-bearing waves 

 through air in the umbra and penumbra will probably obey laws 

 different as regards absorption and refraction from those obeyed 

 in illuminated air. In the second place, the strength, frequency 

 and character of natural electric waves, and of atmospheric dis- 

 charges, may vary. The variations may occur either because the 

 propagation of natural waves from distant sources is facilitated or 

 impeded by the eclipse, or, possibly, because the production of 

 natural electric waves or atmospheric discharges is for some un- 

 known reason affected by the eclipse. 



