Oology may be said to be the latest of the sciences; and although perhaps not a very profound one, it is certainly among the most interesting. Those who are not ornithologists, or specially interested in natural history, can have but little idea of the progress made of late in all that pertains to the nidification of British birds. Expensive and elaborately illustrated treatises have been written on the subject; naturalists have spent thousands of pounds in tracking birds to their breeding haunts; and some of the best scientific workers of the day are devoting their lives to this and the kindred subject of migration. Then again city "naturalists" have their continental collectors, and are building up quite a commerce about the subject. The money value of a complete set of clutches of eggs of British birds is about £200, although more than double this sum would be given for eggs taken within the British Islands. Of course a great number of birds do not breed and never have bred here; for whilst the number of species comprising the home list is three hundred and sixty-seven, only about two hundred breed within our shores. Not a few of the eggs of British birds are worth more than their weight in gold, whilst those of certain species which are supposed to have become extinct bring quite fabulous prices. A well-marked pair of golden eagle's eggs have been known to fetch £25. The market value of an egg of the swallow-tailed kite is three guineas, of Pallas's sand-grouse thirty shillings, while ten times that amount was recently offered for an egg of this Asiatic species taken in Britain. On the other hand, the eggs of certain of the social breeding birds are so common in their season as to be systematically collected for domestic purposes. And this in face of the fact that many of them are remarkable alike for size, shape, and beauty of colouring. This applies particularly to the guillemot, whose eggs are often remarkably handsome. As a rule the colour of these is bluish green, heavily blotched, and streaked with brown or black; and the form that of an elongated handsome pear. The guillemot is one of our commonest cliff-birds, and is found in greatest abundance at Flamborough Head. The eggs are systematically gathered by men who are let down the rocks in ropes. They traverse the narrowest ledges, placing the eggs which they gather daily in baskets fastened round their shoulders. The guillemot makes no nest, lays but one egg, and incubation lasts about a month. The birds sit upright, and when suddenly alarmed, as by the firing of a gun, the eggs fall in showers into the sea. Most of those collected at Flamborough are sent to Leeds, where the albumen is used in the preparation of patent leather; whilst the eggs taken on Lundy are used at Bristol in the manufacture of sugar. At the British breeding-stations of the gannet, or Solan goose, thousands of birds breed annually, though in numbers less than formerly. In this case the