Vol. XVII, No. n 



WASHINGTON 



November, 1906 



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MATEONM 



M&AM 



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THE AMERICAN ECLIPSE EXPEDITION 



By Rear Admiral Colby M. Chester, U.S.N., Retired 



Formerly Superintendent of the U. S. Naval Observatory and Com- 

 mander-in-Chief of the American Eclipse Expedition of 1905 



f h ^HE American Eclipse Expedition 



■ nf TfinS WP^ <~h^ larcrpst nnp that 



m was ever fitted out by any na- 



tion, and I have had difficulty in gleaning 

 from the mass of scientific data resulting 

 from its work a gist of the matter which 

 in a popular form I shall endeavor to 

 place before you tonight. 



In studying the records of parties who 

 had observed eclipses of the sun, it be- 

 came evident to me that the larger the 

 number of instruments and observers that 

 could be put into the field the better was 

 the chance for procuring results, provided 

 the observers were properly educated for 

 the work. It also appeared that the 

 military training of a man-of-war's crew 

 gave them many of the qualities required 

 for the observers, who were to take ad- 

 vantage of the important few moments 

 during which the sun can be eclipsed, and 

 I endeavored to procure as many men to 

 select from as possible. This assumption 

 was strongly fortified by the experience 

 of Sir Norman Lockyer, the distinguished 

 astrophysicist of England, who has writ- 

 ten extensively of his association on 

 eclipse work with the British navy. In 

 the navy men arc trained for years to 

 prepare for the one important battle, pos- 



sibly of a lifetime, which may last but for 

 a few brief moments and v et the results 

 of which may make or ruin a nation. The 

 importance of training for this event can- 

 not therefore be overestimated. 



Likewise an eclipse of the sun can 

 cover but a short period of time, and but 

 few of such events which can be properly 

 observed occur in any one man's profes- 

 sional experience. It is necesary, then, 

 to make thorough preparations if we 

 would get from these rare occasions the 

 full benefits which may be derived from 

 them. 



HOW ECLIPSES ARE CAUSED 



It is hardly necessary to go into the 

 theory of eclipses with this audience to 

 make clear the operations undertaken by 

 the eclipse expedition of 1905, and with- 

 out being didactical I will simply explain 

 why we go so far as Spain to observe a 

 total eclipse of the sun. 



It is well known that an eclipse of the 

 sun is caused by the moon passing in its 

 orbit between that body and the only 

 known people from whom its view can be 

 shut out. Now the sun is about four hun- 

 dred times as far away from our in- 

 habited globe as is the moon. By an in- 



An address to the National Geographic Society, March 30, 1906. 



