328 CONSTRUCTION OF CATALOGUES. 
able but that one half of the lists published have 
been formed without regard to the circumstances 
causing the residence or visits of animals; nor is it 
doubtful, but thatin asserting that an animal is scarce 
or frequent, the authors of these lists have over- 
looked the fact that it is one scarce or frequent in 
the country as a whole, or scarce or frequent in 
many countries conjointly. Supposing a bird stated 
in books, and known to be found generally as a 
common inhabitant of England to be recognised 
as such in any provincial list, it is clear that no 
knowledge is this communicated; and supposing 
that in any other district it was found not quite so 
common, and yet reported as common in the orni- 
thological catalogue of that district, it is obvious 
that the truth is kept back. In short, the manner 
of these communications is altogether far too general, 
and deficient in the necessary precision. If such 
terms as “ common,” “ scarce,” and the like, be not 
used relatively, and if there be not precision used 
in referring to the occurrence of animals, but little 
information is imparted by these lists, and I think 
also that their value would be doubled,if to the bare 
intimation of the frequency or scarcity of occur- 
rence relatively to the aggregate of each animal 
respectively, there were added the causes in oper- 
tion, and a reference to the conditions by which 
the number ts controlled. 
