The Past and Coming Transits and Arctic Explorations. 307 



sufficed to deprive the explanation of all real value ; but it was further 

 noted, by Continental and American astronomers, that the whole 

 process by which explanation was attempted corresponded to what 

 school boys call "fudging," or working backwards from the answer to 

 the data of the question, with " allowances for error," whenever any 

 discrepancy seemed disposed to make an appearance. =J' Nevertheless 

 it was not doubted that the " black-drop " is a real cause of difficulty aud 

 error in observing contacts, and very elaborate preparations were made 

 to overcome this difficulty. Models of the transit were constructed, 

 both in Europe and America, on different plans — one devised by a 

 Continental astronomer, the other by the American astronomers in 

 Washiuffton. Elaborate theories were devised to account for the 

 peculiarities and varieties of the observed phenomena, and it was 

 judged, not without reason, that the "black-drop" would not cause 

 the same degree of trouble during the transit of 1874, as it had 

 occasioned in 1761 and 1769, or at least to the mathematicians who 

 had to deal with the results then obtained. 



But when the transit was actually observed, it was found that the 

 " black drop" was a much less serious cause of trouble than another, 

 which, though recorded by observers in 1769, had somehow received 

 much less notice than it deserved. Professor (jrant, in his fine work, 

 "The History of Physicial Astronomy," thus describes what was 

 known of the phenomenon in question before the recent transit : 



"It was remarked, by several observers of the transits of 1761 and 

 1769, that both at the ingress and egress, the portion of the limb of 

 the planet that was off the sun was visible by means of a faint light 

 surrounding it in the form of a, ring. La Chappe, who observed the 

 transit of 1761, at Tobolsk, in Siberia, states that the light of the 

 ring was of a very deep yellow near the body of the planet, but that 

 it became more brilliant towards the outer border. MM. Stromer, 

 Mallott, Bergman, and Melander, who observed the same transit at 

 Upsal, remarked that when three-fourths of the planet's limb had 

 entered upon the sun, the remaining fourth was visible by means of a 

 faint ring which appeared around it. A similar phenomenon was 

 observed on the same occasion by Wargentin, at Stockholm, by Plan- 

 mann, at Cajenburg, aud in several other instances. Dr. Maskelyne, 

 who observed the ingress of Venus upon the sun's disc at Greenwich, 

 on the occassion of the transit of 1769, states that, when the pjanet 

 was little more than half entered upon the sun, he said her whole 



* For instance, the difference of seventeen seconds just mentioned was inferred from the 

 result repaired, not from the facts given. 



