196 Total Eclipse of August 7, 1869. 



Report by Lewis Swift, Esq. 



Marathon, N. Y., Aug. 12,1869. 

 Prof. G. W. How//,, 



Dear Sir : I herewith send you, as chief of our party, a 

 report of my observations on the Eclipse of August 7th, 

 as observed by me at Mattoon, 111. 



I shall describe the phenomena just as they appeared 

 to me and nearly in the order in which they occurred. 



The telescope used, has a 4.5, in. objective and a 

 focal length of 6 feet, mounted temporarily for the occa- 

 sion as an altitude and azimuth instrument. The eye- 

 piece used gave a power of 36. 



About two hours before the eclipse, I marked on a cir- 

 cular disk the positions of four of the principal solar spots, 

 numbered «, 6, c, and d, in the order in which they were 

 severally occulted by the advancing edge of the moon. 



The device used to do this, and also to measure the 

 position of the protuberances, was constructed for the occa- 

 sion as follows : 



Two circular sheets of metal of 6 and 8 inches in dia- 

 meter, concentrically placed upon each other, w r ith a disk of 

 card board between them, was graduated to 5° of arc. 

 The centre was pierced with a hole equal to the size of the 

 screw on the spring tube which holds the eye-piece, and 

 which, w r hen screwed into its place, holds it firmly. In the 

 focus of the eye-piece was a wire, and on the eye-piece was 

 soldered a brass spring, reaching to the graduated circle, 

 and carrying a pencil parallel with the wire, which when re- 

 volved with the pencil inserted would trace a continuous 

 mark ; the design being to lift it while passing a protube- 

 rance, the space left, not only showing the position, but 

 also its width. 



