1869.] The Transit of Venus in 1874. 373 



and (viii) in the above table. But besides the four remaining 

 phenomena I take into account the passage of the earth's centre 

 across the circles, because Mr, Hind's elements are calculated only 

 for these phenomena, and without considering them I should have 

 been unable to test the accuracy of my own conclusions by com- 

 paring them with his results. 



Thus the eight phenomena corresponding to the positions of 

 the earth, nmnbered 1 to 8 in Fig. 2, correspond to — 



(1) External contact for the earth's centre at ingress. 



(2). Internal contact most accelerated at ingress. 



(3) ,, as seen from the earth's centre. 



(4) „ most retarded. 



and the four corresponding phenomena at egress. 



The treatment apjilied to these phenomena has been the fol- 

 lowing: — Takmg Mr. Hind's epochs for the external contacts at 

 ingress and egress, I have thence calculated all the remaining 

 epochs and the position-angles (NOl, N02, &c., Fig. 2) ; the exact 

 agreement of my estimates of such of these elements as Mr. Hind 

 has calculated with the results he has obtained has sufficed to 

 establish the correctness of the mode of operation. Thus has been 

 formed the following table, in which the numbers 1, 2, 3, &c., refer 

 to the figures in Fig 2 : — 



Epoch. Position-angle. 



1, Dec. 8, 13b. 4Giu. 56s KOl = 130" 33' 



2, „ 14 3 59 .. .. K02 = 133 56 



3, „ 14 15 57 .. .. N03 = 136 28 



4, „ 14 29 5 .... N04 = 139 26 



.. .. N05 = 168 58 



.. .. N06 = 166 



.. .. N07 = 163 28 



.. .. N08 = 160 5 



The results thus obtained have been appKed to the formation of 

 Figs. 1 and 2 (Plate), in the following manner : — 



Eejecting phenomena 1 and 8 as no longer concerning us, the 

 triple sets of phenomena 2, 3, 4, and 5, 6, 7 (see Fig. 2), are alone 

 considered. Properly speaking, we should form an orthographic 

 projection of the earth as supposed to be seen from the sun at each 

 of the six epochs corresponding to these phenomena. But no error 

 of importance will be introduced if we take the epochs of the two 

 central passages, 3 and 6. All that will be necessary is to re- 

 member that in considering accelerated or retarded ingress, the 

 earth in Fig, 1 (Plate) must be supposed rotated backwards or 

 forwards respectively, through the arc due to about 12 minutes' or 

 13 minutes' rotation respectively, while corresponding charges must 

 be supposed applied to the earth, as seen in Fig. 2 (Plate), at the 



