Thus, on the whole, we may accept Dr. Davey's opinion--who had good opportunities for observation--that the snake-charmers control the cobras by working upon the well-known timidity and reluctance of these animals to use their fangs till they become virtually tame. FOOTNOTES: [130] _Account of the United States_, vol. ii., p. 9. [131] April 11, 1870. [132] See Bingley, _Animal Biography_, vol. ii., p. 406. [133] Smiles, _Life of Edwards_, p. 124. [134] _Passions of Animals_, p. 229. [135] _Naturalist on the Amazon_, pp. 285-6. [136] _Ibid._ The astonishing facts relating to the migration of turtles in the laying season will be treated under the general heading 'Migration' in my forthcoming work. [137] _Gleanings_, vol. i., pp. 163-4. [138] The tortoise which has gained such immortal celebrity by having fallen under the observation of the author of the _Natural History of Selborne_, likewise distinguished persons in this way. For 'whenever the good old lady came in sight, who had waited on it for more than thirty years, it always hobbled with awkward alacrity towards its benefactress, whilst to strangers it was altogether inattentive.' [139] This gentleman was Lord Arthur Russell. [140] The _Times_, July 25, 1872. [141] See _Annas. and Mag. of Nat. Hist._, 2nd series, vol. ix., p. 333. [142] Thompson, _Passions of Animals_, p. 118; see also Bingley, _Animal Biography_, vol. ii., pp. 447-8. [143] _Natural History of Ceylon_, p. 314. [144] Tennent, _loc. cit._, p. 299. CHAPTER X. BIRDS. ADEQUATELY to treat of the intelligence of birds a separate volume would be required; here it must be enough to deal with this class as I shall afterwards deal with the Mammalia--namely, by giving an outline sketch of the more prominent features of their psychology. _Memory._ The memory of birds is well developed. Thus, although we are much in the dark on the whole subject of migration--so much so that I reserve its discussion with all the problems that this presents for a separate chapter in my next work--we may at least conclude that the return of the same pair of swallows every year to the same nest must be due to the animals remembering the precise locality of their nests. Again, Buckland gives an account of a pigeon which remembered the voice of its mistress after an absence of eighteen months;[145] but I have not been able to meet with satisfactory evidence of the memory of a bird enduring for a longer time than this.