OXYGEN GAS OYSTFR. 



383 



jar of the gas not holding above three pints or a 

 quart. Phosphorus, on being previously lighted in a 

 pendent spoon, and lowered into a jar of oxygen gas, 

 burns with the 'evolution of a light so intense as 

 scarcely to bear being looked upon with the naked 

 eye. During the burning, in each of these instances, 

 the oxygen is consumed ; and the products of the 

 combustion, except in the case of the iron, are sub- 

 stances possessed of acid properties. Oxygen gas is 

 equally powerful in sustaining animal life by respira- 

 tion. If an animal be confined in a given quantity of 

 it, it will live four or five times longer than a similar 

 animal will do in the same volume of atmospheric 

 air. If, again, an animal be confined in a gas which 

 cannot afford oxygen to it, it immediately dies. It is 

 found that a quantity of oxygen gas always disap- 

 pears, or is consumed during respiration, and is in- 

 dispensable to the continuance of life ; and atmo- 

 spheric air, or any gas, sustains life only from the 

 oxygen it contains, and is capable of affording to the 

 blood. Pure oxygen gas, however, is not well 

 adapted to animal existence. If an animal be con- 

 fined in a given quantity of it, its respiration becomes 

 hurried and laborious before the whole of the oxygen 

 is consumed ; and it dies even though so much oxy- 

 gen is present, that another animal, of the same spe- 

 cies, introduced into the residual air, will live. From 

 whence it appears, that pure oxygen proves too 

 highly stimulating for animal life. As mixed in our 

 atmosphere, it is precisely adapted to the support of 

 animal existence. The oxygen forms only one-fifth 

 of its weight, and is diluted with a large volume of 

 another gas, of an opposite or negative quality. (See 

 Nitrogen.) Oxygen gas has been administered, with 

 good effects, in diseases of the thorax, in paralysis, 

 general debility, &c. A remarkable case was that 

 of a large dog, that had been, for several hours, 

 completely drowned, and yet, in consequence of an 

 injection of this gas into his lungs, was perfectly 

 restored to life and all his functions in a very short 

 time. Oxygen has a very powerful attraction for 

 most of the simple bodies, and there is not one of 

 them with which it may not be made to combine. 

 The act of combining with oxygen is called oxidation, 

 and the bodies, after having united with it, are said 

 to be oxidized. The compounds, so formed, are di- 

 vided, by chemists, into acids and oxides. The first 

 division includes those compounds which possess the 

 general properties of acids, and the second compre- 

 hends those which not only want that character, but 

 many of which are highly alkaline, and yield salts 

 by uniting with acids. The phenomena of oxidation 

 are very variable. It is sometimes produced with 

 great rapidity, and with the evolution of heat and 

 light, as in the case of the iron wire above alluded 

 to; on other occasions it takes place slowly, and 

 without any appearance of heat or light, as is exem- 

 plified by the rusting of iron when exposed to a moist 

 atmosphere. All inflammable or combustible sub- 

 stances derive their power of burning in the open air 

 from their affinity for oxygen. The changes expe- 

 rienced by burning bodies are no less remarkable than 

 the alteration which appears in the oxygen in which 

 they are burned. While the oxygen loses its power 

 of supporting combustion, the inflammable substance 

 lays aside its combustibility, becoming an oxidized 

 body, and incapable of being burned again, even in 

 pure oxygen. It has also acquired an addition to its 

 weight. It is an error to suppose that bodies lose 

 any thing while they burn. The materials of our 

 fires do, indeed, disappear ; but when, by means of a 

 suitable apparatus, we detain the products of the 

 combustion, it is found that they weigh more than 

 the inflammable matter that ha- been burned ; and 

 the increase in weight is exactly equal to the quantity 



of oxygen which has disappeared during the process. 

 For many years before the discovery of oxygen gas, 

 all combustible bodies were supposed to contain a 

 certain principle, which was called phlogiston, to the 

 presence of which was ascribed their combustibility. 

 It was supposed that when a body burns, phlogiston 

 escapes from it ; and that, when the body has lost 

 phlogiston, it ceases to be combustible, and is then 

 a dephlogisticated or incombustible substance. A 

 metallic oxide was consequently regarded as a sim- 

 ple substance, and the metal itself as a compound of 

 its oxide with phlogiston. The heat and light which 

 accompany combustion were attributed to the rapi- 

 dity with which phlogiston is evolved during the pro- 

 cess. The discovery of oxygen, and the experiments 

 of Lavoisier, overthrew this doctrine. On burning 

 phosphorus in a jar of oxygen, he observed that a 

 considerable quantity of the gas disappeared, that the 

 phosphorus gained in weight, and that the increase 

 of the latter exactly corresponded to the loss of the 

 former. That oxygen is really present in the oxi- 

 dized body, he proved by a very decisive experiment. 

 Some liquid mercury was confined in a vessel of oxy- 

 gen gas, and exposed to a temperature sufficient for 

 causing its oxidation. The oxide of mercury, so 

 produced, was put into a small retort, and heated to 

 redness, when it was re-converted into oxygen gas 

 and fluid mercury, the quantity of the oxygen being 

 exactly equal to what had combined with mercury 

 in the first part of the operation. 



OYER AND TERMINER (French, to hear and 

 determine,) in English law, is a court held by virtue 

 of the king's commission, to hear and determine all 

 treasons, felonies, and misdemeanors. This commis- 

 sion is usually directed to two of the judges of the 

 circuit, and several gentlemen of the county ; but 

 the judges only are of the quorum, so that the rest 

 cannot act without them. (4 Black. 269.) See 

 Assizes. 



O YES (corrupted from the French oyez, hear ye) 

 is an expression used by the crier of a court, in order 

 to enjoin silence when any proclamation is made. 



OYSTER ; a well known edible shell-fish, belong- 

 ing to the genus ostrea, occurring in most parts of the 

 world. The European oyster (0. edulis), which forms 

 a considerable article of trade on the coasts of Eng- 

 land and France, is generally taken by dredging, 

 after which the animals are placed in pits formed for 

 the purpose, furnished with sluices, through which, 

 at spring tides, the water is suffered to flow. In 

 these receptacles., they acquire the green tinge so 

 remarkable in the European oyster, and which is 

 considered as adding to their value. This colour, 

 which at one time was supposed to be owing to some 

 mineral impregnation, has recently been ascertained 

 to arise from the conferva, and other marine vege- 

 table matter, on which the animal feeds. In many 

 E laces, oysters are planted, as it is called ; that is, 

 irge artificial beds are formed in favourable situa- 

 tions, where they are permitted to fatten and in- 

 crease. The breeding time of oysters is in April or 

 May, from which time to July or August, the oysters 

 are said to be sick, or in the milk. This is known 

 by the appearance of a milky substance in the gills. 

 Oysters attain a size fit for the table in about a year 

 and a half, and are in their prime at three years of 

 age; though what the natural term of their lives 

 may be, it is difficult, if not impossible, to determine 

 with any degree of accuracy. Many curious discus- 

 sions have arisen as to whether oysters possessed the 

 faculty of locomotion. It is well known that, in 

 general, they are firmly attached to stones, or to each 

 other ; and it has been stated, and generally believed, 

 that they are not endowed with any powers of chang- 

 ing their position. From the observations and expe- 



