cxxviii 
LIFE OF WILSON. 
The " Memoir on the Migration and Torpidity of Swallows," wherein Dr. 
Barton was confident he should be able to convince every candid philosopher 
of the truth of his hypothesis concerning these birds, never issued from the 
press, although so publicly announced. And who will venture to say that he 
did not, by this suppression, manifest his discretion? When "Wilson's volume, 
wherein the swallows are given, appeared, it is probable that the author of the 
'"Fragments" was made sensible that he had been writing upon subjects of 
which he had little personal knowledge; and therefore he wisely relinquished 
the task of instructing philosophers, in these matters, to those uioi-c capable 
than himself of such discussions. 
Naturalists have not been sufficiently precise when they have had occasion 
to speak of torpidity. They have employed the term to express that torpor or 
numbness, which is induced by a sudden change from heat to cold, such as is 
annually experienced in our climate in the month of March, and which fre- 
quently affects swallows to so groat a degree as to render tliem incapable of 
flight. From the number of instances on record of these birds having been 
found in this state, the presumption has been that they were capable of passing 
into a state of torpidity, similar to that of the Marmots, and other hybcrnating 
animals. 
Smellie, though an advocate for migration, yet admits that swallows may 
become torpid. "That swallows," says he, "in the winter months, have 
sometiuues, though very rarely, been found in a torpid state, is unquestionably 
true. Jlr. Collinson gives the evidence of three gentlemen who were eye-wit- 
nesses to a number of sand-martins being drawn out of a cliff on the Rhine, 
in the month of March, 1702." * One should suppose that Smellie was too 
good a logician to infer that, because swallows had been found in the state de- 
scribed, they had remained in that state all winter. A little more knowledge 
of the subject would have taught the three gentlemen observers, that the poor 
swallows had been driven to their retreat by cold weather, which had surprised 
them in their vernal migration; and that this state of numbness, falsely called 
torpiiUtij, if continued for a few days, would for ever have destroyed them. 
It is now time to resume the subject of Wilson's Ornithology, as the reader 
will, probably, consider that we have transgressed the limits which our digres- 
sion required. 
Dr. Drake, in his observations upon the descriptive abilities of the poet 
Bloomfield, thus expresses himself : " Milton and Thomson have both intro- 
duced the flight of the sky-lark, the first with his accustomed spirit and 
sublimity; but probably no poet has surpassed, either in fancy or expression, 
the following prose narrative of Dr. Goldsmith. ' Nothing,' observes he, 
' can be more pleasing than to see the Lark warbling upon the wing; raising 
its note as it soars, until it seems lost in the immense heights above us ; the 
note continuing, the bird itself unseen ; to see it then descending with a swell 
as it comes from the clouds, yet sinking by degrees as it approaches its nest; 
the spot where all its affections are centred ; the spot that has prompted all 
* Philosophy of Natin-al History, chap. 20. 
