PRESIDENTIAL ADDRESS. 15 
called a diffraction phenomenon, though it does occur when 
a thin sheet of light from the edge of the sun passes the 
edge of the moon at the moment of totality. The diffrac- 
tion bands would necessarily move onward over the earth’s 
surface with the same relative speed as that of the moon 
and the earth, approximately a mile a second, whereas the 
observed shadow bands have a velocity of only a few feet 
or yards per second. On the other hand, the bands may 
be considered as phenomena of interference of rays of light 
slightly inclined by reason of the irregular refractions ina 
non-homogeneous atmosphere. 
M. Deslandres directed the Bureau des Longitudes 
Mission to Burgos, where the actual duration of visible 
totality was curtailed by clouds to one minute, which did 
not include either the second or the third contacts. The 
proposed photographing of the chromosphere spectrum was 
therefore impossible. Photometric observations of the 
corona were obtained, and M. d’ Azambuja was able to 
measure the corona radiation, obtaining figures which were 
decidedly lower than those obtained by M. Charbonneau in 
1900. M. Kamapell obtained four photographs of the 
corona polarised by reflection. M. Blum obtained two 
photographs of the corona through coloured screens so 
arranged as to transmit only the gaseous radiation of the 
prominences. By comparing these with the ordinary photo- 
graphs, it will probably be possible to determine whether 
or not the prominences emit a more intense continuous 
spectrum than that emitted by the surrounding regions. 
At El Arrouch, 32 km. from Philippeville, M. Andover 
simply attempted to obtain as many direct photographs of 
the phenomena as possible. His instrumental equipment 
consisted of a photographic objective of 14 em. (5°6 inch) 
aperture and 60 cm. (24 inch) fecal length, mounted with 
two enlarging cameras which increased the diameter of 
