September Itli, 1820. 27 



best mode of observation. In consequence of their results, 

 measures were adopted which, in viewing the eclipse, placed 

 the observer in total darkness, the only light admitted from 

 without, passing through the telescope ; although by other 

 means it could occasionally be introduced, and also the general 

 appearance of external objects observed. Circumstances, 

 however, did not permit of proving the efficacy of this arrange- 

 ment, with regard to the primary object in which it originated. 

 The atmosphere, which during the early part of the 7th had been 

 clear and serene, as the morning advanced became gradually 

 overcast by numerous aggregations of loose floating clouds. 

 These continuing to move slowly towards the N.N.W., had 

 nearly disappeared by mid-day, at which time the thermometer 

 stood at 68° in the shade, and soon after twelve a few dense 

 clouds only remained near the zenith towards the S.E. One of 

 these dark masses extending directly over the sun, a few minutes 

 before the expected commencement of the eclipse, completely 

 obstructed the view for the space of 15'. The appulse took 

 place during this interval, and on emerging from the cloud, a 

 dark crescent of the moon's orb was distinctly visible on the 

 sun's disc. This was the last cloud that passed, and through- 

 out the whole duration of the eclipse, the luminaries were not 

 again obscured even for a moment, but a serene and unclouded 

 sky constantly prevailed. 



On first viewing the body of the moon, its irregular and in 

 many places deeply serrated circumference was very plainly dis- 

 cernible. By applying a higher power to the telescope, the 

 unequal magnitudes and varied forms of these inequalities were 

 distinctly to be marked, although there was merely a very 

 attenuated circular segment visible. As the dark orb continued 

 to advance, these irregularities became every moment more 

 conspicuous, exhibiting the appearance of alternating eminences 

 and depressions, in every respect similar to the mountains and 

 valleys on the surface of the earth ; while from the strong con- 

 trast of their shaded outline, their limits and extent could be 

 traced with the greatest precision. Owing to the progressive 

 motion in that direction, these projections on the south-eastern 



