SCIENTIFIC SUMMARY. 
297 
itself, be conclusive evidence against tbe truth of the deduced value or the 
logic of the method applied. 
It will be observed that although these rules refer specially to the transit 
of 1769, they are applicable, with but slight alteration, as rules for the 
guidance of astronomers in dealing with the observations made upon the 
coming transits. The last two are laws which those who deal with ob- 
servations on any subject whatever should hold in constant remembrance. 
In applying these rules to M. Powalky’s case Mr. Stone proves irresistibly 
that little value can be attached to results founded on a mode of treatment 
so irregular as that which M. Powalky has applied to the transit of the last 
century. After adducing a number of instances in which rules 3, 4, and 5 
are broken through, he remarks, we knew, before M. Powalky’s paper ap- 
peared, that by adopting different data different results could be obtained. 
What we did not know was any cause for these discrepancies. The selection 
of the material had been based upon no intelligible principle, and no one 
had been able to reconcile the whole of the durations.” It is the especial 
property of Mr. Stone’s treatment of the subject that every observation of 
durations is represented, that one constant principle is used throughout, and 
that the truth of this principle is not founded merely upon Mr. Stone’s 
opinion, but upon the way in which at every step of the work it is confirmed 
by results. 
The Transit of Venus in 1874. — Mr. Proctor states that the places at 
which the ingress and egress of Venus will be most affected by a parallax 
during the transit of 1874 are situated as follows : — 
(i.) The place at which first internal con- 
tact is most accelerated lies in . . 
(ii.) The place at which first internal con- 
tact is most retarded lies in . . . 
(iii.) The place at which last internal con- 
tact is most accelerated lies in . . 
(iv.) The place at which last internal con- 
tact is most retarded lies in . . . 
Lat. 
Long 
CO 
CD 
o 
45' 
N. 
143° 
23' 
W. 
44° 
27' 
S. 
26° 
27' 
E. 
64° 
47' 
S. 
114° 
37' 
W. 
62° 
5' 
N. 
48° 
22' 
E. 
These places are separated from those which the Astronomer Poyal had 
obtained (by considering passages of Venus’s centre in place of internal con- 
tacts), by 314'0, 920‘2, 764*5, and 208 *7 miles respectively. 
M. Puiseux, Mr, Proctor, and the Astronomer Poyal on the coming Transits. 
— The views which have hitherto been accepted respecting the treatment of 
the approaching transits by the method of durations, and which we quoted 
in our last summary, must, it would seem, be modified. M. Puiseux and 
Mr. Proctor, having calculated the circumstances of the coming transits with 
reference to this method, have come to the conclusion, that so fiir from fail- 
ing totally in the case of the transit of 1874, it may be applied with great 
advantage. Mr. Proctor even asserts that it is better than tlie method 
founded on differences of absolute time in the occurrence of ingress or 
egress as seen from widely separated stations. In a note on the subject, 
Mr. Airy expresses the opinion that M. Puiseux’s researclies fail to exhibit 
tlie method of duration as superior to the method of absolute time dif- 
ferences j but he admits that the former method is one which it is desirable 
