OXY 



OYS 



salifiable bases. Oxidation is often 

 attended willi the evolution of heat 

 and light, as in all processes of com- 

 bustion in atmospheric air ; some- 

 times it is slow, and unattended with 

 such phenomena, as in the gradual 

 rusting of metals. Oxygen is a most 

 powerful supporter of combustion ; 

 it constitutes one fifth of tlie bulk of 

 the atmosphere, and is the principle 

 which enables combustible bodies to 

 burn in it. The product of combus- 

 tion, that is, the oxide or acid, is 

 sometimes itself gaseous, as when 

 charcoal, by burning, is converted 

 into carbonic acid ; or it is liquid, as 

 hydrogen, by combustion, produces 

 water ; or it is solid, as when iron, 

 by burning, produces oxide of iron. 

 Oxygen gas is also essential to res- 

 piration ; that is, to the evolution of 

 carbonic acid from the blood ; but 

 requires to be diluted with nitrogen, 

 as in the air, otherwise it destroys 

 life by producing over-activity. Seeds 

 cannot germinate without oxygen, 

 and are, therefore, not to be buried 

 too deep in a compact soil. The 

 leaves of trees, also, cannot perform 

 their functions without its presence, 

 although they are always exhaling a 

 large quantity of this gas. Oxygen 

 is very extensively diffused in na- 

 ture ; in the compound state it forms 

 eight ninths of all waters, and at 

 least one half of all structures, wheth- 

 er mineral or organic, except a few 

 oils and resins. 



OXYGENATION, AERATION. 

 The introduction of atmospheric air 

 into the blood through respiration. 



OXYHYDROGEN BLOWPIPE. 

 A contrivance for burning hydrogen 

 gas in an atmosphere of pure oxygen, 

 whereby the most intense heat is ob- 

 tained. Dr. Hare's apparatus is con- 

 sidered equal, if not superior, to most 

 others. 



OXYMEL. A mixture of honey 

 and vinegar, for coughs. 



OXYMURIATES, OXYCHLO- 

 RIDES. An erroneous name for 

 salts of chlorine, formerly called ox- 

 ymuriatic acid. 



OX- YOKE. The timber placed 

 above the heads of oxen, and fasten- 

 550 



ed by a throat-latch or piece, to yoke 

 them. The French fasten a flat 

 board to the foreheads ; and it is 

 found best to have one for each ox, 

 as shown in the Figure. Harness- 



ing oxen in the same way as horses, 

 if they be well broken, is a very su- 

 perior method, and highly recom- 

 mended in hilly countries, where it 

 has been practised from time un- 

 known, as in AVales, Cornwall, and 

 Devonshire in England. 



OXY- SALTS. Chemical com- 

 pounds containing an acid and alkali, 

 which are both oxides. This class 

 of salts comprehends the greater part 

 of those used in the arts. 



OXYURES. A family of hyme- 

 nopterous insects with an external 

 ovipositor resembling a tail. They 

 are pupivorous, and prey on other in- 

 sects. A genus of intestinal worms, 

 also. 



OYSTERS. Ostracea. A family 

 of inequivalve bivalves, of which the 

 Ostrca edulis, or common oyster, is an 

 esteemed luxury. Those from the 

 Chesapeake Bay are best. They are 

 frequently transplanted and set in 

 beds in the North and East Rivers, 

 and elsewhere, divided by stakes, in 

 shallow water, within reach of the 

 tide ; water which is only partially 

 salt is best. They grow sufficiently 

 for use in two or three years. They 

 should not be di.sturbed in May, which 

 is the spawning season, but are fit to 

 eat in August. 



OYSTER SHELLS. They con- 



