OOLACHAN, or EULACHON. See CANDLE-FISIt.
ObLITE, 5'4-lit (from Gk. oon, egg Xleos, lithos, stone). A term formerly used a, synonymous with Jurassic, but now used to designate the middle and upper divisions of the Jurassic rocks, the lower division being called the Liss. In the United States the 061ite is of little importance, and in fact has only been iden tified along the Pacific coast, but in Europe it underlies a vast area, for during this period of geologic time there occurred one of the greatest encroachments of the sea over Europe and Asia which is known in geologic history. The rocks of the (161ite period are chiefly limestones. They are perhaps hest known from their occurrence in the 'Jura Mountains of Switzerland, where the rocks have been bent into such beautiful folds as to attract the attention of the most casual ob server. See Julusste SYSTEM.
OoLOGY, 4-61'4-ji (from Gk. oon, egg + -Ncryia, -logia, account. from Neyeiv, to say). The of eggs; especially the study of the breeding habits, nests, and eggs of birds; a branch of ornithology. Birds' eggs (q.v.) are conveniently classified as 'marked' and 'un marked,' according to the ground color. Birds which lay their eggs in holes in trees or in the ground almost always have white, unspotted eggs, and they are frequently of a peculiarly smooth, translucent texture. Birds which build in trees generally have blue or greenish eggs, either spotted or unspotted, while birds that build in bushes, near tlw ground, are likely to lay speckled eggs. The shore-birds usually have the eggs heavily marked with (lark brown on a yellowish background, while gulls and terns al ways lay heavily marked eggs. Ducks, geese, and herons lay unspotted („.. Sonic ldrds lay only a egg, and this is especially true of cer tain marine birds, such as auks, guillemots, and louvres. Others lay two eggs, notably the hum ming-birds, while three, four, and five are the common numbers. When the number is more than eighteen, there is reason to believe that more than one female has been concerned in the laying, as happens among ostriches and mound-birds. Gallinaceous birds and ducks, coots, and rails lay"Ihe largest number of eggs; the quail is said to lay eighteen, the coot fifteen. the wood duck fourteen, and the sons sixteen.
There is no direct relation between the size of the bird and the size of the egg. The smallest eggs actually, and proportionately also, are those of humming-birds. which may less than half an inch long by one-third of an inch wide. The largest eggs actually are those of the ostrich, but proportionately the egws of the kiwi and mound-birds are larger. Of North Ameri can birds, the largest eggs are probably those of the California condor, which are 4.5 X 2.5 inches. The swan lays an egg nearly as large, hut does not breed within the United States. The great auk. though a much smaller bird than either of these, laid an egg 5X3 inches; hut very few of them are now• in existenve. (See GAREFowl..) The study of birds' nests is sometimes called ealiology, as distinguished from oology proper. See NIDIFICATION.
Dr. Thomas M. Brewer (q.v.) may well he called the father of American o6]ogy, for his North American Oology, a quarto which appeared in 1857, was the first systematic work dealing with that subject published in this country.
Unfortunately only one part of this was ever printed, but it is notable for its colored plates of birds' eggs. Capt. Charles E. Bendire (q.v.) became famous as an oblogist in the West, and in 1883 was appointed a curator in time National Mu seum. In July, 1892, appeared the first volume of his Life 1Hi,stor•ies of North American Birds, and the second volume appeared in September, 189G. They are quarto volumes of many hundred pages and numerous colored plates. An earlier descriptive work was Ernest Ingersoll's N'ataral History of the Veils mid Eggs of incrican Birds, of which seven 'parts,' describing the nidifi cation of about 100 species of oscine birds, with colored plates of their eggs, were issued at Salem, Mass., in 1879-80. Other books dealing exclusive ly with American oblogy have been: Gentry, Nests and Eggs of North American Birds (Phila delphia, 1885) : and Davie, Nests and Eggs of North American. Birds (2d ed., Columbus, 1889). Several fine works describe the eggs of European and East Indian birds, of which one of the oldest and finest in English is Hewitson's (3d ed., Lon don, 18.56). For others consult Newton, Diction ary of Birds (London and New York, 1893-96). See Eno, and the accompanying colored plates.