24 
On Residual Phenomena . 
[January, 
this difficulty. Certain suggestions, may, however, be given. 
In case of a theory or a law which is correct, and which 
fully embraces and accounts for all the faCts, the discrepan- 
cies will be very minute ; they will be smaller in proportion 
as the experimentalist is more skilful, and they will further 
decrease as suitable precautions are taken and sources of 
error are eliminated. In the case of a false theory, on the 
other hand, the errors will be much larger, will vary in 
different instances, and, instead of being reduced by improved 
methods and more finished manipulation, are more likely to 
become greater. Residuals differ from both these cases : the 
correspondence between the faCt and the theory cannot to a 
certain extent be denied, but there is a margin which, though 
generally small, is constant, and cannot be lessened by any 
niceties and refinements of procedure. Where the law or 
the theory under investigation is merely qualitative, more 
must be left to the taCt and judgment of the observer. 
In carefully searching for the source of an anomaly 
we may discover someting other and much greater than we 
originally intended or hoped. The old apologue of the 
farmer’s sons — who by digging for an unknown treasure 
increased the fertility of their land, and reaped a harvest of 
unimagined luxuriance — finds its frequent realisation in the 
history of scientific research. 
We shall, perhaps, find it instructive to turn from the 
consideration of residual phenomena which have been recog- 
nised as such, and which have been fully traced to their 
causes, and examine certain laws which admittedly do not 
fully agree with the phenomena, and whose shortcomings 
demand explanation. Such laws may, of course, belong to 
our second class, and in that case require total rejection ; but 
they may possibly be not so much erroneous as incomplete, 
embracing a part only of the phenomena, and leaving the 
rest still unaccounted for. 
Considerable attention is now drawn to the relations 
existing between the atomic weights of our received ele- 
mentary or simple bodies. If these bodies have been evolved 
from a common source, as a variety of considerations con- 
spire to suggest, it is highly probable that such relations 
should exist. If, on the other hand, they are primordially 
distindt, and, as far as we can perceive, accidental in their 
number, in their distribution, their relative amounts, and 
their properties, — suppositions highly repugnant to our intel- 
lect, — then no laws of numerical relation between their atomic 
weights may be traceable. 
The earliest attempt in this direction was made by Prout. 
