[81] We must not confound _true nocturnal_ nightingales with those which are called _mopers_. A true nocturnal sings from night to morning without stopping, while a moper sings only at intervals, unconnectedly, and always makes pauses of some minutes between each strain. All nightingales become mopers when they reach five or six years of age; whence arises the mistake of many persons, who think they possess a nocturnal when they have really only a moper. The reverse happens sometimes, also; for a true nocturnal bird, caught such, often loses his power after one or two years of captivity, and is then a mere moper.--AUTHOR. [82] It must, however, be owned, that of twenty young nightingales bred from the nest scarcely one succeeds in all respects. They seldom possess their natural song in its purity; they almost invariably introduce, in spite of all their instruction, foreign and disagreeable tones. The young which are caught in the month of August, before their departure, are the best; they have already learnt their father's song, and they perfect it the following spring, if they are placed beside a good singer.--AUTHOR. [83] "A nightingale which I had given away," says M. Le Manie, "no longer seeing his mistress, left off eating, and was soon reduced to the last gasp; he could not support himself on his perch! but being restored to his mistress, he revived, ate, drank, perched, and had recovered in twenty-four hours. It is said that some have been known, when set at liberty in the woods, to return to their masters." It is quite certain that they recognise the voice of their masters and mistresses, and approach at their call. [84] According to the Greeks, Progné was metamorphosed into a nightingale, and Philomel, her sister, into a swallow. The Latins have changed and confused this story, which the moderns have, in their turn, copied without examination. [85] It is not a native of Britain.--TRANSLATOR. [86] To prepare this tincture, take of water four parts, of black oxide of iron one part; boil the oxide with the water, and then pass a current of chlorine gas through the mixture till it will absorb no more; filter the liquor and evaporate over a slow fire to the consistence of an extract; when this is cold, pour upon it of hydrochloric ether three parts; let it macerate without heat for several days; then add of alcoholised hydrochloric acid nine parts; macerate again, filter the liquor, and expose it to the sun.--TRANSLATOR. [87] This is a mistake; it is as fond of berries as of insects.--TRANSLATOR. [88] This bird also has the art of pleasing by his pretty tricks. He shows a striking affection for his mistress; utters a particular sound, a more tender note to welcome her; at her approach he darts against the wires of his cage, and, by a continued fluttering, accompanied with little cries, he seems to express his eagerness and gratitude.