( 602 ) 
of rotation of the wing did not coincide with the centre of the 
moon’s dise but with a point nearly on the moon’s limb. 
Consequently this plate shows details of the corona on only one 
side, moreover the image is diffused in the direction from East to 
West, probably owing to an irregularity in the motion of the driving 
clock of the coelostat. 
Nr. 5 (120 sec. Lumière jaune) shows the same want of sharpness, 
which here also exists in the direction from North to South. Pro- 
minences and „Bailey's beads” are elongated and useless. 
Nr. 6 has little value owing to direct sunlight. | 
B. Spectrographs. 
I. Three Prism Spectrograph (f = 1.1 a). 
An exposure of 340 seconds on a panchromatic plate of LUMIERE 
has not given the slightest trace of the spectrum of the corona. 
The width of the slit was 1/4 mm. On this plate and on the one 
exposed immediately afterwards, air-spectra of 20 to 60 sec. exposure 
are very well measurable, some of them have even been over-exposed. 
Also the iron-spectrum given by a small coil and Leyden battery 
in 3.5 minutes is well measurable. The plate is entirely fogged, 
which is evidently due to the development, since the edges, which 
were not exposed, are also fogged. The plate cannot have been 
spoiled or stale, since proof-plates taken from the same batch and 
exposed on the preceding days are very clearly developed, and are 
entirely clear up to the edges. The matter is at present entirely 
inexplicable, since at all events the clouds should have given a 
spectrum. 
IT. Two Prism Spectrograph (f = 3.5 a). 
The exposure with this instrument has entirely failed, the assistant 
charged with the control of the running plate having lost his pre- 
sence of mind. The plate shows very strongly the spectrum of the 
last crescent of the sun (exposure 5* on moving plate). It has 
however been stopped exactly in the moment when the first flash 
spectrum was to be impressed on it, though according to the pro- 
gramme it ought to have moved on for another 5 seconds. The plate 
has then remained unmoved for some time and shows, adjacent to the 
above mentioned spectrum, a strongly over-exposed spectrum, by which 
everything in the neighbourhood is fogged. Next the plate ought 
to have been brought to its middle position for the exposure of the 
corona. In this operation the lines of H and Ca have just been 
