44 TRANSIT OF VENUS, 1874. HONOLULU. 



black drop nor ligament. The planet was perfectly circular, and nothing 

 whatever disturbed the sharpness of its outline at the place of contact. The 

 band of light [after a certain interval] gradually and imperceptibly brightened, 

 and as Mr. Clapp said " twenty " it was sufficiently bright to induce me to 

 consider the contact as established [by which I meant quite passed]. The 

 clock time for this is 20 h . 46. 20 S- 0. At that instant the general appearance 

 was similar to the model a second or two after contact, as nearly as possible 

 as represented in Fig. 2, Plate IV., which was drawn an hour or two 

 afterwards.* 



On concluding the micrometer-measures given below, that is, about half 

 an hour after internal contact, I wrote some notes in the observing-book, 

 including the following : 



" At the 20 seconds which I have recorded I am perfectly certain the 

 contact was passed, established completely not ' contact ' properly speaking, 

 for that implies some definite instant which was never observed. At that 

 time, and for a second or two before, there was the sliadmu on the light at the 

 point of contact, a phenomenon always seen with the model, but nothing like 

 a ligament or black drop, although I looked carefully for such an appearance." 



Much disheartened at the unsatisfactory nature of the observation of 

 contact I withdrew from the telescope to look through the record of times, 

 and at my request Mr. Clapp took my place and scrutinised the planet. I 

 asked him if he could see a fringe of any kind near the periphery of the 

 planet, of shadow surrounding it, or diffused light within. He said he saw 

 nothing but a plain black sharply- defined circle. I called Major "Wodehouse 

 in also (not being able to commence " limb " measures immediately), and 

 called his attention to the same points with the same result. 



I then replaced the double-image micrometer, and made the following 

 series of measures of the distance between the near limbs of the Sun and 

 planet, and of the diameter of the planet, reversing the direction of measure- 

 ment at 20 h . 55 m . and at 21 h . 2 m . when the position of the movable half-lens, 

 with reference to the fixed half-lens, was changed, as indicated by a line 

 drawn between the measures. At each change the telescope was re-pointed, 

 to bring the point of contact exactly in the center of the very limited field of 

 view, and the direction of measurement re-adjusted. It is here that the want 

 of a position- circle is most felt. 



* In the reproduction of this diagram for the Astronomer Royal's " Parliamentary Keport " the 

 lithographer has incorrectly introduced a dark shadow between the limbs. Fig. 2, Plate IV., is a 

 correct copy of the original sketch. 



