388 SCIENTIFIC RECORD FOR 1883. 



with an hour-axis two meters long, carrying a strong and large plat- 

 form, upon which were fastened the following photographic apparatus : 

 a large camera having a lens of eight inches (0.21 m.), made by Darlot, 

 giving a field of 20° of 25° (plate of 0.40 m. by 0.50 in.), and designed 

 for photographing the corona and the region about the sun with reference 

 to the stars there found. A second camera, with a Darlot lens of six 

 inches (0.16 m.) giving a field of 26° to 35° (plate of 0.30 m. by 0.40 in.), 

 for the same purpose ; and a very fine apparatus by Steinheil for study- 

 ing the corona. A second mounting carried several cameras with lenses 

 of four inches (0.10 m.), giving a great amount of light, and designed to 

 determine by very sensitive plates what are the limits of the corona — 

 an apparatus of great light-power, the exposure lasting during the whole 

 of totality." 



For spectrum analysis the following apparatus was employed : "A 

 [reflecting] telescope of 0.50 m. aperture, having a very short focus 

 (1.60m.), and supplied with a direct-vision spectroscope of ten prisms; 

 the slit of the spectroscope could be placed at different position-angles, 

 and rapidly opened or closed at the pleasure of the observer. An ex- 

 cellent finder, supplied with a reticule, was placed near the spectroscope, 

 and distant from it by such an amount that, when one eye had fixed 

 upon some point of the corona in the finder, the other could obtain the 

 spectroscopic analysis of this point." There were also attached to this 

 telescope a bi-quartz polariscope by Prazmowski, and a spectroscope for 

 showing Eespighi's rings. A spare mirror of 0.40 m. diameter was carried 

 as a reserve, but was not brought into use, as by great care the first 

 was kept uninjured, in spite of the frequent rains and the moist climate. 



Mr. Janssen gives the following condensed report of his own observa- 

 tions, drawn up immediately after the observations, in accordance with 

 the plan by which all the observers of the party were governed : 



" My observations were of two classes — optical and photographic. The 

 optical observations were principally designed to determine whether the 

 coronal spectrum consists of a continuous spectrum as a background 

 with bright lines, or if the Frauenhofer lines exist there generally (an 

 investigation made especially with regard to the question of ultra solar 

 cosmic substances). In 1871 1 had announced that, besides the hydro- 

 gen lines, I had established in the spectrum of the corona the presence 

 of the D line and of several others. 



"In the present eclipse I proposed especially to solve this question. 

 By means of the optical arrangements above described, I have been 

 able to determine that the basis of the coronal spectrum is composed of 

 the complete Frauenhofer spectrum. The principal lines of the solar 

 spectrum, especially J), b, JB, etc., were detected so surely that there can 

 be no possible doubt of this fact. I recognized, perhaps, a hundred 

 lines. 



"I recognized this composition of the spectrum, particularly in the 

 lower or most brilliant portious of the corona, but not to an equal degree 



