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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 u allowance for 
error,” whenever any discrepancy seemed disposed to make an 
appearance.* Nevertheless it was not doubted that the “ black 
drop ” is a real cause of difficulty and error in observing con- 
tacts, and very elaborate preparations were made to overcome 
this difficulty. Models of the transit were constructed, both in 
Europe and in America, on different plans — one devised by a 
Continental astronomer, the other by the American astronomers 
at Washington. Elaborate theories were devised to account for 
the peculiarities and varieties of the observed phenomena. And 
it was judged, not without reason, that the 66 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 
Girant, in his fine work, “ The History of Physical 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 surround- 
ing 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, Mallet, 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 Planmann at Cajen- 
burg, and in several other instances. Dr. Maskelyne, who 
observed the ingress of Venus upon the sun’s disc at Green- 
wich, on the occasion of the transit of 1769, states that, 
when the planet was little more than half entered upon the sun, 
* For instance, the difference of seventeen seconds just mentioned was in- 
ferred from the result required, not from the facts given. 
