82 CALIFORNIA ACADEMY OF SCTEMCES, [Proc. 3D Ser. 



irradiation." One observer has given detailed drawings of 

 the form of the "beads," and exhibits them with mechan- 

 ical precision and hardness; as a matter of fact he was not 

 a draughtsman nor a skilled observer, and yet his name 

 carried great weight. Ci v^ v $i.<y4^o/^ 



Similar Phenomena at Transits of Venus and Mer- 

 cury ACROSS the Sun's Disc. 



In our observations of the transit of Venus, December 

 1882, at Cerro Roblero, New Mexico, 5,676 feet above the 

 sea, and 1,655 feet above the Rio Grande del Norte and the 

 great arid plain of the Jornado del Muerte, there were, 

 towards the close, occasional tremors or shiverings of the 

 borders of the discs of the Sun and planet from slight 

 tremulousness of our atmosphere; but the eye was not con- 

 fused, as would have been the case if the discs had con- 

 tinued ill-defined and unsteady by excessive vibration. In 

 the first case the eye could and did select its opportunity 

 for micrometric measurements. But at this very period the 

 assistant astronomer in charge of the photographic expo- 

 sures reported the results unfavorably affected by this 

 slight unsteadiness. It was a case where the eye selected 

 a moment of steadiness, but the mechanical movement of 

 the photographic shutter permitted no selection. The un- 

 steadiness of the atmosphere at the time between the third 

 and fourth contacts permitted a beautiful and unique exhi- 

 bition of the fine, white, faint, crescent of coronal light 

 apparently surrounding part of the disc of Venus as an illu- 

 minated atmosphere. The crescent was long, extremely 

 thin, white, and as fine, sharp and regular as if cut by the 

 finest graver; and we watched it die away in excessive mi- 

 nuteness. We made drawings of the exhibition. Another 

 observer of this beautiful phase of the transit at a different 

 station saw a similar phenomenon "shortly after the first 

 external contact, when the limb of the planet was 'boiling," 

 and "it was difficult to be certain whether it lay within or 

 without the planet's contour * * * but it certainly ap- 

 peared to extend at any rate within the circumference; and 



