recollect, not without regret, that in June, 1746, I was visiting for a week together at Spalding, without ever being told that such a curiosity was just at hand. Pray send me word in your next what sort of tree it is that contains such a quantity of herons' nests; and whether the heronry consists of a whole grove or wood, or only of a few trees.

It gave me satisfaction to find we accorded so well about the caprimulgus; all I contended for was to prove that it often chatters sitting as well as flying, and therefore the noise was voluntary and from organic impulse, and not from the resistance of the air against the hollow of its mouth and throat.

If ever I saw anything like actual migration, it was last Michaelmas-day.* I was travelling, and out early in the

*The subject of migration appears to have been a very favourite one with our author, occupying the greater part of many of his subsequent letters, and evidently often the subject of his private thoughts. He sometimes seems puzzled with regard to the possibility of many of the migrating species being able to undergo the fatigue of long or continued journeys; and often wishes almost to believe, though contrary to his better judgment, that some of these enter into a regular torpidity. We find torpidity occurring among animals, fishes, the amphibia, and reptiles, and among insects; but we have never found any authenticated instance of this provision taking place among birds. Their frames are adapted to a more extensive locomotive power; and the change to climates more congenial to their constitutions, preventing the necessity of any actual change in the system, is supplied to those animals deprived of the power for extensive migration, by a temporary suspension of the most of the faculties which, in other circumstances, would be entirely destroyed. Birds, it is truc, are occasionally found in holes, particularly our summer birds of passage, in what has been called a torpid state, and have revived upon being placed in a warmer temperature; but this, I consider, has always been a suspended animation, where all the functions were entirely bound up as in death, and which, by the continuance of a short period, would have caused death itself—not torpidity, where various functions and secretions, capable for a time of sustaining the frame, are still going on.

The possibility of performing long journeys, as we must believe some species are obliged to do before arriving at their destination, at first appears nearly incredible; but, when brought to a matter of plain calculation, the difficulty is much diminished. The flight of birds may be estimated at from 50 to 150 miles an hour; and if we take a medium of this as a rate for the migrating species, we shall have little difficulty in reconciling the possibility of their flights. This, however, can only be applied to such species as, in their migrations, have to cross some vast extent of ocean, without a resting-place. Many that visit this country, particularly those from Africa, merely skirt the coast, crossing at the narrowest parts, and again progressively advancing, until

morning: at first there was a vast fog; but, by the time that I was got seven or eight miles from home towards the coast, the sun broke out into a delicate warm day. We were then on a large heath, or common, and I could discern, as the mist began to break away, great numbers of swallows (hirundines rustica) clustering on the stunted shrubs and bushes, as if they had roosted there all night. As soon as the air became clear and pleasant, they all were on the wing at once; and, by a placid and easy flight, proceeded on southward, towards the sea: after this I did not see any more flocks, only now and then a straggler.

I cannot agree with those persons who assert, that the swallow kind disappear some and some, gradually, as they come; for the bulk of them seem to withdraw at once; only some stragglers stay behind a long while, and do never, there is the greatest reason to believe, leave this island. Swallows seem to lay themselves up, and to come forth in a warm day, as bats do continually of a warm evening, after they have disappeared for weeks. For a very respectable gentleman assured me that, as he was walking with some friends, under Merton-wall on a remarkably hot noon, either in the last week in December, or the first week in January, he espied three or four swallows huddled together on the moulding of one of the windows of that college. I have frequently remarked that swallows are seen later at Oxford than elsewhere: is it owing to the vast massy buildings of that place, to the many waters round it, or to what else ?

they reach their final quarters; and during this time having their supply of suitable food daily augmented.

The causes influencing the migration of birds, appear more difficult to solve than the possibility of the execution of it. They seem to be influenced by an innate law, which we do not, and cannot, comprehend, though in some measure dependent on the want of food or climate congenial to the system of each, and which acts almost without the will of the individual. Neither this, however, nor the duties incumbent on incubation, can be the only exciting causes, as we may judge by the partial migrations of some to different parts of the same country, where food and the conveniences for breeding are alike ; by the partial migration only, of a species from one country to another, differing decidedly in temperature, and where the visiting species thrives equally with the resident one; and by the males of some species migrating, while the females remain.-W. J.

When I used to rise in a morning last autumn, and see the swallows and martins clustering on the chimneys and thatch of the neighbouring cottages, I could not help being touched with a secret delight, mixed with some degree of mortification: with delight, to observe with how much ardour and punctuality those poor little birds obeyed the strong impulse towards migration, or hiding, imprinted on their minds by their great Creator; and with some degree of mortification, when I reflected that, after all our pains and inquiries, we are not yet quite certain to what regions they do migrate; and are still farther embarrassed to find that some actually do not migrate at all.

These reflections made so strong an impression on my imagination, that they became productive of a composition that may perhaps amuse you for a quarter of an hour when next I have the honour of writing to you.

LETTER XXIV.

TO THE SAME.

SELBORNE, May 29, 1769.

DEAR SIR,-The scarabæus fullo* I know very well, having seen it in collections; but have never been able to discover one wild in its natural state. Mr. Banks told me he thought it might be found on the sea-coast.

On the 13th of April, I went to the sheep-down, where the ring-ousels have been observed to make their appearance at spring and fall, in their way, perhaps, to the north or south; and was much pleased to see three birds about the usual spot. We shot a cock and a hen; they were plump and in high condition. The hen had but very small rudiments of eggs within her, which proves they are late breeders; whereas those species of the thrush kind that

It is properly the melolontha fullo. Mr. Bennett says that all the specimens of this noble chafer that have yet been captured in England, have occurred on the coast of Kent, Dover appearing the middle point of their range.-ED.