The American Eclipse Expedition 



CQI 



it was thought that by choosing a site for 

 one eclipse station in the central and 

 another in the eastern section, if bad 

 weather affected the observations of one 

 it might not the other, and out of the two 

 stations we would procure at least one set 

 of observations. 



Records indicated that the north coast 

 of Africa was also comparatively free of 

 storms at this time of the year, and as 

 good harbors existed on its 

 coast, affording suitable 

 means for the transship- 

 ment of delicate instru- 

 ments, one station was lo- 

 cated in Algeria, at Guelma. 

 This locality was elevated 

 about 1,500 feet above the 

 sea, was far enough back 

 from the Mediterranean to 

 avoid its sometimes foggy 

 conditions, and yet it was 

 easily reached by railroad. 

 The selection of this sta- 

 tion was fortunate in many 

 respects. 



MONTHS OF PREPARATION 



Several months before 

 the expedition started, in- 

 struments were prepared 

 and set up at the naval ob- 

 servatory, most of them 

 being newly designed or 

 rebuilt for the occasion. 

 All the apparatus was con- 

 structed as perfectly as in- 

 genuity and skill could 

 make it. 



In order that during: the 



was put in charge of instrumental con- 

 struction, and before the expedition sailed 

 all new instruments and practically all 

 that had been used on previous occasions 

 were set up and tested. 



A new lens of 7^2 inches aperture and 

 65 feet focal length, composed of three 

 pieces of glass, was purchased for the 

 occasion as well as for future use at the 

 observatory. The two outer lenses are of 



bnel 



maximum Lime Oj 



minutes and 42 seconds of 

 totality as many photo- 

 graphs of the eclipse phe- 

 nomena might be taken as possi- 

 ble, the mechanism must be arranged to 

 go without a hitch and the people in 

 charge of instruments made confident by 

 frequent drills that all parts would work 

 smoothly and quickly. Mr VV. W. Din- 

 widdie, one of the assistants, who was 

 well fitted by natural mechanical ability 

 as well as by experience for the work. 



Making Sketches During Eclipse 



flint glass, covering a double convex lens 

 of crown glass. The flint glass is of two 

 different varieties, enabling the optician 

 to correct for both the red and blue end 

 of the spectrum. Thus the lens is abso- 

 lutely achromatic, and both the ordinary 

 or orthochromatic plates can be used with 

 it to equal advantage. This is not the 

 case with the ordinary lens, composed of 



