4 86 



NA TURE 



March 22, 1906 



AMERICA'S OBSERVATIONS OF THE TOTAL 

 SOLAR ECLIPSES OF 1900 ASD 1901. 1 



IN the year 1900 the moon's shadow swept across 

 the southern portion of the United States of 

 America, travelling from New Orleans, through 

 Georgia, South and North Carolina, and leaving this 

 continent at Cape Henry, in Chesapeake Bay. After 

 traversing the Atlantic Ocean the shadow crossed 

 Spain, and cut the African coast at Algiers. 



The large strip of country in America over which 

 the shadow passed drew a great number of American 

 observers to this region, and in a volume which has 

 quite recently been published we have a detailed 

 account of the observations and photographs. 



For the main part, this valuable addition to eclipse 

 literature deals with the observations made by the 

 Naval Observatory, which equipped two stations on 

 the central line, one in North Carolina and the other 

 in Georgia, the intention being to duplicate the work 

 in order to minimise the danger of unfavourable 

 weather. Since, however, a large number of other 

 parties with varied equipments was scattered along 

 the line of totality, the reports of several of these have 

 been included in a separate section of this volume. 



The stations fixed upon by the Naval Observatory's 

 parties were two in the State of Georgia, namely, 

 Barnesville and Griffin, and one in North Carolina, 

 Pinehurst being the location selected. The reason 

 why two stations were chosen in the former State was 

 because it was desirable to concentrate the spectro- 

 scopic attack on the chromosphere near the end of 

 the shadow track, Griffin being the region where the 

 lower strata of the sun's atmosphere during totality 

 were exposed longer to view. Griffin was twenty 

 miles distant from Barnesville. Prof. Updegraff was 

 placed in charge of the Georgia stations, while Prof. 

 Skinner superintended the work at Pinehurst. 



Fortunately the weather was very favourable at all 

 the stations, so that the results here brought together 

 are numerous and very complete. First, as regards 

 the instrumental equipment at each of the stations. 

 Space does not permit reference to the instruments 

 in anything like detail, but the reader will find in the 

 volume all the information clearly set out. The 

 general scope of the work undertaken will, neverthe- 

 less, be gathered from the following brief summary 

 concerning the chief instruments employed. 



Barnesville. — This station was chiefly used for 

 photographing the corona. The largest instrument 

 employed there was an object-glass of 4-inch aperture 

 and 4o'-feet focal length, the tube being pointed directly 

 at the sun at eclipse time. The image formed was 

 4. }6 inches in diameter. 



"Another instrument consisted of a battery of cameras 

 mounted on a wooden polar axis 11 feet long and 

 moved by a clepsydra. The cameras erected on this 

 were as follows -.—three lenses of 6-inch aperture 

 having focal lengths of 104, So, and 33 inches; a 

 4-inch Dallmeyer lens of 17-inch focal length ; and a 

 3.5-inch Dallmeyer of 9.5-inch focal length. 



In addition, there were two 5-inch equatorials for 

 visual observations and a prism-spectrograph. 



Griffin. — At this station the attack was made from 

 the spectroscopic point of view. Here were located 

 a 10-feet concave Rowland grating worked in con- 

 junction with a 3.5-inch quartz lens and a coelostat ; 

 the plates used were placed in curved backs, and the 

 first-order spectrum was employed. There was also 

 a large Rowland concave grating of 21.5-feet radius, 

 worked also in connection with a quartz lens and 

 ccelostat, but mounted after the method of Rowland. 



I " Publication* of ihe U.S. Naval Observatory." Second Series, vol. vi , 

 appendix i. By Rear-Admiral Colby M. Chester, U.S.N., Superintendent. 

 Washington, 1905.) 



NO. 1899, VOL 73] 



This was implored chiefly for the ultra-violet in the 

 second-order spectrum. 



Pinehurst. — Here was erected a 5-inch 40-feet 

 coronagraph pointed directly at the eclipsed sun. 

 Worked in connection with three independent coelo- 

 sials were : — a plane grating objective spectrograph 

 with ruled surface 3-5x5 inches (15,000 lines to an 

 inch); a concave (10-feet) grating slit spectrograph 

 similar in ruling and size to the plane one ; and a 

 4-inch prismatic camera with one flint glass prism 

 of 6o°. 



As at Barnesville, a large polar axis was here 

 erected to carry several cameras, and two Dallmeyer 



Fir,. 1. — The coronas of 1900 (uppir) and 1901 (lowerl as photographed by 

 the U.S. Naval Observatory parties. (The ncrth point of the sun is 

 at top of each.) 



lenses of 38-inch focal length and a Voigtlander lens 

 were mounted on it. Three equatorials for visual 

 observations and a transit instrument completed the 

 equipment. 



In the volume before us the results obtained with 

 each of the several instruments are individually dis- 

 cussed, and on the whole they have turned out very 

 satisfactory. Further, the volume is illustrated, not 

 only by a series of excellent reproductions from photo- 

 graphs of the crimps and the instruments in situ, but 

 of the forms of the corona and the chromospheric 



