The Sand Martin. 
398 
[July, 
it seems to come to the day , or at any rate two or three days 
will fairly embrace their variation from the appointed time. 
Observations extending over many years induce us to expe 
them here on the 15th or 16th of April.* No doubt the con- 
dition of the weather has some effedt upon this regularity o 
appearance, but very much less than it might rea ®°^ bly , ® 
expedted to have; and it will, I think, be found that the 
effedt of weather upon the arrival of our British Hirundines 
has a relation rather to their numbers than to the mere tad 
of their appearance at a certain date. In the case oi the 
other species — the house swallow, martin, &c. there wii 
generally be found a considerable instalment about the 
usual time given in the Natural-History Calendars ; but it 
the season should be cold and stormy (as indeed it often is) 
the numbers of the first arrival will be reduced to a mini- 
mum. It may be remarked, however, that occasionally, in 
bad weather, the numbers seem to go on increasing ioi 
some time after the first arrivals are noted. . 
The migration of birds has been often and justly cited as 
affording the most striking and wonderful evidence of the 
operation of Divine Wisdom in allotting to the. creatures, 
for a special end, an insight far transcending their ordinal y 
intelligence. And in the modification of that instinct, and 
its subservience to actual circumstance, as in the case we are 
now considering, there is a striking manifestation of the 
power of Him who governeth all things in heaven and 
earth. A too close consideration of the unity of Natuie, 
and of the ordinary working of the Almighty Artificer, may 
tend, with some minds, to darken through familiarity the 
truth that “ Nature’s law ” presupposes a Law-giver: it is 
well, then, to consider also attentively the exceptions and 
variations from her ordinary course, inasmuch as the character 
and end of a law is often revealed to us by its interruptions. 
It has been thought by some naturalists that swallows 
send forth scouts in advance of the main body, to examine, 
at the time of their migration, the climate of the country 
that they purpose visiting. And when we consider the dis- 
tance of the countries to which they migrate, and the 
very great difference of climate existing between their sum- 
mer and winter habitations, this appears not an unwarrant- 
able supposition. It is, indeed, hard to imagine any other 
way of accounting for the delay of their main body when 
the weather is exceptionally severe in spring. And this is, 
to me, a much more reasonable way of accounting for the 
* An article in the “ Globe ” lately placed the arrival of swallows about a 
week or ten days later. But my date, as given above, has been verified. S.B, 
