The earliest account of these nests is met with in Bontius, who tells us that "Large flocks of very small birds of the Swallow kind come down during the breeding season, and settle upon the Chinese coasts, where they swarm over the cliffs that overhang the sea. In these situations they build their strange nests, forming them of fish spawn, which they collect from the shore. These nests are much valued by the natives, who will often pay very large sums of money for them, in order to make them into soup, which is considered a dainty." More modern investigators have been equally inaccurate in their surmises, some pronouncing them to be constructed of the flesh of a kind of snail or worm, or a peculiar species of sea-weed, gathered from the shore. Recent observations upon this interesting point have, however, proved that all these explanations are incorrect, and we learn that these luxuries, in which the Chinese so much delight, are formed of a secretion resembling saliva, drawn from under the bird's own tongue. After a great variety of experiments as to its component parts, Marsden pronounces that the material resembles a mixture of gelatine and white of egg, an opinion in which Bernstein, who is a trustworthy authority on this disputed question, entirely coincides; we will, however, describe the nest of the Salangane before we give our readers the real secret of its construction, as vouched for and described by the last-mentioned naturalist. The Salangane usually builds in such deep and dark cavities that the observation of its proceedings as it fastens its small, thin, gelatinous nest to the rock, is attended with great difficulty. This structure is in shape like the quarter of an egg-shell, divided longitudinally along its entire length. Some of these nests are white, some of a brown colour, and opinion differs considerably as to the reason of this variety; we ourselves believe it to depend on the age of the structure, as we have never seen a brown nest occupied, but other authorities pronounce them to be the work of two distinct species. In the markets the white nests command a very high price, while such as are dark are but little esteemed. The two white eggs laid by the Salangane are deposited at the bottom of this remarkable gelatinous receptacle, without any further preparation for their warmth or comfort. THE KUSAPPI. [Illustration: THE WHITE-THROATED PRICKLY-TAILED SWIFT (_Acanthylis caudacuta_).]