TEANSIT OF VENTJS. 105 



from one to the other as quickly as possible ; and even if it did 

 break, we have the facts clearly made out that the drop was seen 

 Im. 45s. after ingress, and that although it appeared nearly equal 

 to the semi-diameter of the planet iu length, yet it was certainly 

 not more than one-twenty-second part of the diameter, as shown 

 by the photograph. 



On comparing the time of No. 9 Janssen plate, after allowing 

 20s. lost in taking it out, with Mr. Vessey's time of contact, it 

 appears that the drop at egress was seen Im. 45s. before contact, 

 or was in fact about the same length as at ingress. 



Mr. AUerding, chronometer maker, "of Hunter-street, also saw 

 the drop most distinctly, and watched it through the various 

 phases till it broke. He was using at the time a very good 8^-inch 

 achromatic telescope, but to aA'oid sun-light and heat he had 

 reduced the aperture to 2 inches, and with this small opening he 

 obtained very satisfactory definition of the sun and ])lanet. 

 Unlike Mr. Hirst, who observed in the beautiful atmosphere of 

 the mountains, Mr. AUerding observed from the back yard of his 

 house in Hunter-street, which is surrounded by houses. In a 

 report of his observations, which he has furnished to me, he says — 

 " At the internal contact at ingress I saw a drop which formed 

 into a cone, and when this had nearly disappeared it seemed to 

 stretch out to a fine thread (see diagrams), to which Yenus seemed 

 to be attached. The thread appeared hard and definite, without 

 any hazy margin, and I estimated its length at one-third the 

 diameter of the planet. It then instantaneously disappeared at 

 12h. 24m. 44s., and Yenus appeared already well detached from 

 the sun's limb. Had I not Avaitcd for the disappearance of the 

 fime line, I would have made inner contact at least thirty seconds 

 sooner." JSTow, in this case we have no Janssen photographs to 

 show how long the drop was, but we have other observations 

 taken in Sydney which prove that the drop seen by Mr. AUerding 

 was equal in length only to the space moved over by the planet 

 in forty-five seconds ; that is, 1"7 seconds of arc from the sun's 

 limb — or two-and-a-half times the length Mr. Stoi^ie estimates 

 it to be. I cannot see any satisfactory explanation of these facts. 

 "What cause could magnify the length of the drop, even if it 

 had a real existence, from one-twentieth to one-third the diameter 

 of the planet, I am at a loss to conceive ; or why, of three 

 telescopes of small aperture two should exhibit the drop and 

 the other not I am also at a loss to explain, and must for the 

 present at least leave it in uncertainty. 



There are however several observations recorded of a kindred 

 phenomenon that I should like to place on record. At ingress I 

 saw nothing of it, but at egress I saw it distinctly ; and the cause 

 is, I think, easily traced. But to take, first, the observations at 

 ingress. 



