386 SCIENTIFIC RECORD FOR 1883. 



of the landing, the men-of-war steamed away to Tahiti, leaving selected 

 members of their companies to assist in the work. The American party 

 was favored with the help of Messrs. Qualtrough, Dixon, Fletcher, and 

 Doyle, officers of the "Hartford," and often seamen. 



The two weeks preceding the eclipse were occupied in mounting the 

 iustruments and in other preparations. Pendulum observations during 

 this time were made by Messrs. Preston and Brown, under instructions 

 from the United States Coast and Geodetic Survey. The weather was 

 in general pleasant, though there was one severe rain-storm, and nearly 

 every day there were flying clouds with slight showers, as is not unusual 

 in the region of the trade-winds. The wind was usually strong, and blew 

 steadily from a direction varying from north to east, but never south of 

 east, though the island is in the heart of the southeast trade region. 

 Eight inches of rain fell during the seventeen days which the party 

 spent on the island, more than half of this in one storm on May 4. 



The weather on the morning of May 6 was cloudy and threatening, 

 but after several showers the sky cleared shortly before the time of first 

 contact, and remained clear the remainder of the day, with rapidly mov- 

 ing clouds. One of these partially concealed the corona for about twenty 

 seconds in the first minute of totality, and the sun was wholly in a cloud 

 soon after the close of totality; but the observations were not interfered 

 with, though there was at all times baze iD the atmosphere. 



The observations planned were carried out successfully, with results 

 which will be given in full detail in the official report of the expedition. 

 A summary of these results can, however, be given at the present time. 

 Professor Holden swept for intra-mercurial planets, but none existed in 

 the region examined. Spectroscopic observations were made by Dr. 

 Hastings and Messrs. Eockwell, Brown, aud Upton, with interesting 

 results. Dr. Hastings had devised a spectroscope by which the spectra 

 ©f two opposite sides of the sun were brought iuto juxtaposition, and 

 could be examined simultaneously. This instrument, which was attached 

 to a 6£-inch equatorial, was used especially to note the changes in the 

 appearance of the 1474 line on the preceding and following limbs of the 

 sun as the eclipse progressed. At the beginning of totality the 1474 line 

 extended to a height of about 12' on the eastern limb of the sun, while on 

 the western limb it was faint, and not more than 4' in height. As the 

 eclipse progressed, the lines changed relatively, becoming sensibly equal 

 at mid-eclipse, and the conditions at the close of totality being the reverse 

 ©f those at the beginning. This change was many times greater than any 

 change due to the moon's motion, aud is regarded by Dr. Hastings as 

 conclusive proof that the outer corona is mainly due to diffraction. The 

 dark D lines were seen in the corona, and the bright hydrogen and mag- 

 nesium lines by several observers. The relative height and brightness 

 of the coronal rings seen in an integrating spectroscope were estimated. 



The duration of totality was five minutes twenty -five seconds. The 

 corona was bright, aud characterized by five well-defined streamers, a 



