128 L. Trouvelot—Transit of Mercury. 
disc, and this became very apparent a little before five o’clock 
when the seeing was at its best. Then it certainly appeared 
narrower on the preceding side than on the following. At this 
moment I estimated its width on the preceding side at about 
one-twentieth of the diameter of the disc, while on the follow- 
ing it was estimated at about one-fifteenth. Fig. 2. 
Between four and five o'clock, Mercury was spectroscopically 
observed with an excellent diffraction grating which I owe to 
the kindness of Mr. Rutherfurd. The spectrum appeared of an 
intense black color, much darker than any of the absorption 
lines of the solar spectrum, and quite sharply defined on its 
edges. I attentively observed whether the absorption lines 
trum wou ve been visible with a spectroscope of small dis- 
persive power. 
After five o’clock the sky became partly cloudy, and observa- 
tions were difficult. At 5% 54™ the definition was rather bad, 
the image being unsteady and the limb of the sun wave 
3. and boilin minute or two before the third 
of the sun in apparent contact with Mercury had 
= their corners atte off. Fig.3. This phenomenon 
which was very apparent seems to be of the same 
nature as the black drop, which I had not the good 
fortune to see. I do not remember having seen at 
ext this time any trace of the luminous ring either on, 
or outside the sun, but the seeing was bad at this moment, and 
my attention was so much occupied with the last contact that 
very likely it has escaped my notice. 
s already stated, the sun’s limb was wavey and boiling at the 
few seconds later, the planet rea red and was seen § 
notching the sun’s limb, it having probably been lost in the 
ae ee ee 
