THE TRANSIT OF YENUS AS OBSEEYED AT EDEN. 115 



opposite eud B. I attached a piece of wood to the camera so as 

 to project over B. An elastic band secured to the camera below, 

 and enclosing B, was tied by a string to this projecting piece, so 

 as to allow B to move freely within it. When a double image is 

 to be taken, the telescope is so adjusted, by the help of the finder, 

 that a little more than half of the sun shall appear in the photo- 

 graph. The driving clock is then stopped and the photograph 

 taken in the usual way. The telescope remains at rest for a 

 minute ; meanwhile the band which pulled down the flashing 

 shutter is cut with a sharp pair of scissors, and at the end of the 

 minute the string which holds the band at the end B is cut ; B 

 is thus drawn down and A flies up with the flashing shutter, so 

 that a second image is taken. As an elastic band is cut each time, 

 it is necessary to have as many bands round the camera at A, and 

 as many loops of string at the piece over B, as there are double 

 images to be taken. 



On the morning of the 9th the weather seemed promising. I 

 obtained clock signals from the Sydney Observatory, and by 11 

 o'clock we were all collected and anxiously waiting for the transit 

 to commence. Clouds were coming up and the wind rising, and 

 we had reason to anticipate a disappointment. At the time of 

 ingress, however, the clouds had not yet intervened. The exact 

 instant of first contact it was impossible to determine. Mr. Mac 

 Donnell recorded llh. 56m. 29s. Sydney mean time as the moment 

 at which he became quite convinced that the transit had com- 

 menced. I found my 2-inch aperture answer admirably, not 

 only from the diminished light and heat, but also from the great 

 distinctness of the outlines of the sun and planet. I soon became 

 convinced that all we had heard and read respecting the apparent 

 elongation of the planet's disc, and formation of what has been 

 described as the " drop," was a delusion. For some minutes 

 before internal contact I could see clearly the whole of the planet's 

 outline ; in fact, it presented exactly such an appearance as might 

 have been expected from a planet possessing an atmosphere. 

 Whilst the direct light of a portion of the sun was shut out by 

 the intervention of the planet, a sufficient portion of that light 

 reached the eye by refraction, through that atmosphere, to render 

 the whole outline visible. By means of a double-wire position 

 micrometer, I obtained a measurement of the apparent diameter 

 of Yenus ; then, bringing one of the wires into the position of a 

 tangent to the sun's limb, waited until the planet seemed to touch 

 the other wire. This occurred at Oh. 21m. 7s., though Mr. Mac- 

 Donnell, who judged the same phenomenon by the eye, unaided by 

 a micrometer, placed it nearly two minutes earlier, or at Oh. 19m. 

 24s. This I believe to be the most important determination, being 

 the moment of complete ingress ; and I regret that the action of the 

 wind on the telescope rendered it impossible to keep the micrometer 



