126 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



(c.) REPORT OF MR. C. H. ROCKWELL: 

 Tiof. E. S. HOLDEN : 



Dear Siii: At the time of the eclipse of May 6, 1S83, 1 bad a spectroscope with a grating of 

 14,400 lines to the inch attached to a telescope of 4 inches aperture, using a spectrum of the first 

 order. 



The grating was so adjusted that the region from a little below E to F was in tiie field. The 

 slit was narrow, and was not changed; it was set tangential to the limb of the moon. 



I did not notice any flash or other phenomena at the time totality comiiienued. 



Owing, perhaps, to a pg,ssing cloud, 1 did not see the line K 1474 for the first minute and a 

 half; it then came somewhat suddenly very distinctly into view, and I was able to follow it 4' or 5' to 

 the west of the disk of the moon. I repeated this observation a second time with the same result. 



I saw also two green lines, probably magnesium, each of them brigliter and broader than 1474, 

 but much shorter. I saw these two lines each time when I followed 1474 into the corona, but failed 

 to see them when I turned the spectroscope to the north and south sides of the moon. Neither did 

 I see 1474 save on the western side, as already mentioned. 



As compared with the eclipse of July, 1878, observed at Central City, Colorado, I should say the 

 darkness w:is less intense on this occasion. 



It is proper to add, however, that in 1-87S I had been reading a chronometer with the aiil of a 



lantern before looking at the corona, while on this occasion I had not used any artificial liglit for 



any purpose. 



Very resi)ectfullv, 



CHARLES H. ROCKWELL. 



Caroline Island, 1th May, 188.'}. 



id.) REPORT OF MR. ERASMUS D. PRESTON. 

 (PiiblisUeil by periuissiou of the Superiuteudeut of the U. S. Coast iuiil Gcoilotic .Siu-vey.) 



Honolulu, June 1, 1883. 

 Prof. E. S. Holden, 



Chief United States Eclip.^c Expedition : 



Dear Sir: I have the honor to submit you a report of my observations in connection with 

 the Total Solar Eclipse of May 6, 1883. In obedience to instructions from Prof. J. E. Hilgard, 

 Superintendent of the U. S. Coast and Geodetic Survey, I left Washington February 28, and re- 

 IJorted to you in New York the following day. 



During the voyage out some preliminary computations were made. An extended list of stars 

 was selected, suitable for time observations either at Flint or Caroline Island, their factors com- 

 puted and checked,* and pairs of stars were chosen for observati()ns for latitude by the method of 

 ecjual zenith distances. 



The instruments furnished by the Coast and Geodetic Survey are as follows : 



instruments. 



TRANSIT. 



U. S. C. S. Transit No. 2, made by Troughton & Simms, of London, to which a delicate level 

 was attached before leaving Washington, for the determination of latitude. The aperture of the 

 telescope is 2f inches with a focal length of 40 inches, and a diagonal eye-piece- was used giving a 

 magnifying power of 110. The field of view was 12 minutes of arc, one division of striding level — 



* The factors A, B, aud C for a small list of time stars were computed at Madison by Mr. PEJfNOCK, one of my 

 l)upils, aud hauded to Mr. Pkestox for his use. — E. S. H. 



