292 NATURE OF SUBSEQUENT ENQUIRY. 
worthy of some regard in framing an estimate of 
the causes in active influence on the positions, 
ranges, and migrations of our native animals of 
Devon. 
Itis fairly to be presumed that our acquaintance 
wth secondary causes is as yet very imperfect ; at 
least we are still unaware of the reasons of a very 
great nnmber of phenomena which from being pe- 
culiar to certain tribes or to certain species cannot 
possibly be referable to general laws; and until 
some light has been thrown on these circumstances, 
our knowledge on this head must be deemed in- 
complete. 
Upon the whole it will be found difficult to 
render an inquiry into circumstances and detail 
interesting, though the chief objects and questions 
we shall have in view will be—firstly, to determine 
or illustrate general laws if the limits of such an 
investigation should by possibility admit of it ; 
secondly, to determine and illustrate secondary 
laws or causes of geographic distribution by atten- 
tion to the following circumstances,—comparisons 
of the phenomena of this district with others of 
similar extent and similar or dissimilar aspect 
and contingencies, irregular distributions, the oc- 
currence of varieties and other modifications as 
provisions to suit local circumstances, the times se- 
lected for migration, (of the various kinds) with an 
aitention to the causes possibly influencing these 
movements, modifications of habits, peculiarities 
in the Zoology of the whole of the spot selected, or 
in any of its parts, remarkable deficiencies in its 
Zoology, general, numerical, and other results. 
Lastly, it will be right to make mention of a variety 
of other circumstances, though no explanation of 
their occurrence can be given, since records of un- 
explained facts may serve toinvite notice and 
inquiry into causes. 
