An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

OR SCIENTIFIC METHOD. 287
causally connected in any way ; for h may be connected
with other antecedents which co-operate with ABCD.
Many examples which Mill and his followers give as
coming under this canon are really
instances of a
distinct rule, which has been expressed thus : When
any part of a complex phenomenon
plained by the causes which have been assigned, a
is still unex
further cause for this remainder must be sought.
There is no indication in the inquiry, as far as it has
gone, of what this cause may be, and hence the
"
"
Method becomes a finger-post to the unexplained.
It calls attention to "residual phenomena" which have
to be accounted for. Such phenomena have frequently
led to discoveries of the first importance, such as that
of argon by Lord Rayleigh and Professor Ramsay in ,^
1894. Their investigations started from the detection
of an unexplained residual phenomenon :
nitrogen ob
tained from various chemical sources was of uniform
density, but atmospheric nitrogen was about ^ per cent
heavier. They proved that the increased weight was
due to the fact that the nitrogen in the atmosphere is
mixed with an inert gas hitherto undetected. Sir J.
Herschel says: "Almost ail the greatest discoveries in
astronomy have resulted from the consideration of
residual phenomena of a quantitative or numerical
kind. ... It was thus that the grand discovery of
the Precession of the Equinoxes resulted as a residual
phenomenon, from the imperfect explanation of the
return of the seasons by the return of the sun to the
same apparent place among the fixed stars." Herschel s
remarks received afterwards a most remarkable illustra
tion in the discovery of the planet Neptune by Adams
and Leverrier in 1846. The sun and the known
planets have a calculable effect in disturbing the path