IMPORTANCE OF UNIFORM RESULTS. 993 
observation can be relied on as doing, renders it the 
most certain resource in all physical enquiries, 
where the discovery of a general law is desired. If, 
for instance, we found, in ornithology, that twenty 
out of twenty-three sub-families, particularly abun- 
dant in species, could each be divided into seven 
groups or genera, and that each of these subordi- 
nate divisions was in itself circular, we should be 
justified in believing the determinate number to be 
seven ; because the preponderance of evidence sanc- 
tions the conclusion, and leads us to believe that a 
more extended analysis of other groups will produce 
the same result. But if, in the remaining three, 
equally abundant in materials, we can by no pos- 
sibility make out more than five circular divisions, 
we must either seek to equalise the results, or, if 
that fails, abandon our first theory, and commence 
anew. It will not be sufficient to argue that the 
two missing types of these groups may be supplied 
by future discoveries; because such a singular co- 
incidence, of two missing types in each of three 
genera, carries on the face of it a high degree of 
improbability. It will be remembered, also, we are 
now supposing all the groups before us to be perfect ; 
and, if perfect, then without any violent or pal- 
pable interruption in the line of continuity ; in other 
words, presenting no interval, wherein, if these 
missing groups happened to be discovered, they 
could be naturally inserted. Nothing, indeed, can 
be easier than to start a theory on the universal 
prevalence of a determinate number, assumed upon 
the partial arrangement of one or two insignificant 
groups, and without complying with the con- 
