e obviated.

The organisation of the British forces reflected the utmost credit on
the energy and ability of Lieutenant-Colonel Tupman, who was responsible
for the whole. No useful measure was neglected. Each observer went out
ticketed with his "personal equation," his senses drilled into a species
of martial discipline, his powers absorbed, so far as possible, in the
action of a cosmopolitan observing machine. Instrumental uniformity and
uniformity of method were obtainable, and were attained; but diversity
of judgment unhappily survived the best-directed efforts for its
extirpation.

The eventful day had no sooner passed than telegrams began to pour in,
announcing an outcome of considerable, though not unqualified success.
The weather had proved generally favourable; the manifold arrangements
had worked well; contacts had been plentifully observed; photographs in
lavish abundance had been secured; a store of materials, in short, had
been laid up, of which it would take years to work out the full results
by calculation. Gradually, nevertheless, it came to be known that the
hope of a definitive issue must be abandoned. Unanimity was found to be
as remote as ever. The dreaded "black ligament" gave, indeed, less
trouble than was expected; but another appearance supervened which took
most observers by surprise. This was the illumination due to the
atmosphere of Venus. Astronomers, it is true, were not ignorant that the
planet had, on previous occasions, been seen girdled with a lucid ring;
but its power to mar observations by the distorting effect of refraction
had scarcely been reckoned with. It proved, however, to be very great.
Such was the difficulty of determining the critical instant of internal
contact, that (in Colonel Tupman's words) "observers side by side, with
adequate optical means, differed as much as twenty or thirty seconds in
the times they recorded for phenomena which they have described in
almost identical language."[767]

Such uncertainties in the data admitted of a corresponding variety in
the results. From the British observations of ingress and egress Sir
George Airy[768] derived, in 1877, a solar parallax of 8.76" (corrected
to 8.754"), indicating a mean distance of 93,375,000 miles. Mr. Stone
obtained a value of ninety-two millions (parallax 8.88"), and held any
parallax less than 8.84" or more than 8.93" to be "absolutely negatived"
by the documents available.[769] Yet, from the same, Colonel Tu