13 



OBJECT-GLASS. 



OBSERVATION AND EXPERIMENT. ; 





The causes of obesity are both natural and acquired. It is wel 

 known that among domesticated animals some have a greater 

 tendency to accumulate fat than others, and such breeds are kept up 

 for the purpose. In the same way there are human beings who 

 exhibit the same tendency, and in the case of certain individuals the 

 most persevering measures fail to reduce their weight. On what this 

 tendency depends it is difficult to say exactly, but there is reason to 

 believe that it depends upon the food in the early stages of digestion 

 being converted into fat, which getting into, the blood is deposited in 

 the adipose tissue by a kind of excretory process. In such individuals 

 the starch and sugar of the food appear to be more readily convertible 

 into fat than in others. But whilst this tendency may naturally exist 

 it can be greatly increased by diet. There can be no doubt that the 

 class of foods called carbonaceous, starch, sugar, and fat when taken 

 in larger quantities than are required to maintain the heat of the 

 body, are employed in developing the adipose tissue. Experiments on 

 the feeding of animals have shown that in proportion as these sub- 

 stances are employed in the food do they become fat. Alcoholic 

 beverages, when not taken to such an excess as to produce more 

 disastrous results, have a tendency to produce fatness. They act in the 

 first place by stimulating the digestive process, and in the next by 

 preventing that action of the oxygen of the air on the blood and tissues 

 by which the carbonaceous foods are oxygenated and carried off in 

 the form of carbonic acid. Sedentary and indolent habits also have a 

 tendency to produce fatness. As it is by active exertion that the 

 oxygen of the atmosphere is introduced to the tissues of the body, and 

 they are changed and carried away, so if this process be prevented by 

 indolence, the tissues go on developing, and this is frequently the case 

 with the adipose tissue. Heat has also a tendency to develope obesity. 

 Living in warm rooms, or in a warm climate, other things being equal, 

 has a' tendency to produce fatness. 



Whilst obesity is exposed to dangers of its own, a precipitate anxiety 

 to keep it down or prevent it is most earnestly to be deprecated. Th< 

 practice of taking vinegar to prevent obesity is attended with great 

 danger, as it acta by destroying the digestive power of the stomach. Per- 

 sons also frequently put themselves on a short diet, and without not only 

 fat-forming matters but also flesh-forming matters in their food. In this 

 way the heart soon breaks down for want of nourishment, and death 

 occurs in a variety of ways from want of power in the central organ of 

 the circulation. The entering also at once upon a system of hard 

 exercise and short sleep is frequently attended with the death of the 

 patient. The great object of treatment should be the gradual reduc- 

 tion "f tin- fat, whilst the muscular power, especially of the heart, 

 should be maintain^!, One of the most important things to be 

 attended to is the nature of the diet. The amylaceous, saccharine, 

 oleaginous, and alcoholic ports of the diet should be diminished. No 

 butter at breakfast, no bread at dinner, and one glass of wine a day is a 

 good receipt for a healthy fat man who has been in the habit of living 

 riminately. Hard biscuits may also be advantageously sub- 

 stituted for bread. Regular exercise should be taken, never excessive. 

 Sawing, digging, walking and mountaineering according to the weight 

 and strength of the patient are all good. Generally the obese are 

 infirm of will, and this bodily state is perhaps connected with their 

 mental condition, and of all patients they seem leant able to make 

 up their minds to the necessary discipline for their cure. If the per- 

 suasion implied in the sentence of " six months at the treadmill " 

 c mill in any manner be applied in their case, it would undoubtedly 

 be the most effectual remedy. 



OKI I .' T < , I. \ - - The lens or system of lenses nearest the object 

 in a telescope or microscope. As explained under EYE-PIECK. its 

 business is to form a correct image of the object within the tube ; 

 hence it should be free from spherical aberration, and should be 

 achromatic. For the method of rendering it so we must refer to 

 MICROSCOPE, and for a due understanding of the defects, to ABER- 

 RATION in uptics. [ACHROMATIC; LENS; LIGHT.] 



OBLATE, a term applied to a spheroid which is made by the 

 revolution of an ellipse about the smaller of the tw'o axes. 



oHLIQUE. This term is used as opposed to direct or right, and 

 signifies whatever is not direct or right. The word seldom appears, 

 except as expressing that an angle is not a right angle, all other uses of 



almot obsolete. 



i li'.l.loi " ITY, a term used in astronomy to express the angle made 

 by the ecliptic with the equator. The greatest latitude at which the 

 sun ever appears vertical is the obliquity of the ecliptic. [Scs ; 



-SIOX AKD NUTATIOX.] 



OBLONG, a word in common use, expressing the same meaning as, 

 an<1 i" 'i preferable to, the mathematical term rectangular, 



r having the figure of a rectangle. 



Olio)-; (/'a/.), a musical instrument of the pneumatic kind, blown 



it is a tube of boxwood, 22' niches in length, 



dander in the upper part, but spreads out conically at. the lower end, 



nsistfl of three joints, or pieces, besides the reed. Its compass 



is two octaves and a fifth, from c below the treble clef, to o, the fourth 



added line above it : 



' Modern improvements have augmented the resources of the oboe by 

 means of eleven keys, but only skilful performers can safely be trusted 

 to produce the two or three highest notes ; and till very recently, E, or 

 even c, above the staff, was considered the utmost practicable extent of 

 the instrument. Oboes are now frequently made to go down to B fe , 

 in which case they exceed the usual length, and have an additional 

 key. 



The oboe has for centuries past been in use, and may be traced back 

 to the reign of Edward III., in whose band oboes, under the denomi- 

 nation of Wayyhtes, were employed. Indeed our itinerant parish- 

 musicians, the official precursors of what was once a merry season, 

 retain the appellation of Waits, though they have long abandoned the 

 instruments which conferred on them their title. 



Up to nearly the close of the last century, this instrument was only 

 known, in most parts of Europe, by its French name, Hautbois, a word 

 which in England has always been pronounced lloboy ; and this pro- 

 nunciation has been transferred to the Italian term, though the word 

 oboe is now invariably adopted in writing. 



OBOLUS (oj8o\(is), was a Greek coin, both silver and brass. At 

 Athens it was of silver, the sixth part of a drachma, and worth 

 somewhat more than five farthings sterling. The -Eginetan obolus is 

 stated to have been heavier than the Athenian. It is generally 

 supposed that fiMus and obelos (ojSoAfo and oj3f Aifs) were originally the 

 same word differently pronounced, and that the coin obolus was first of 

 iron or copper, in form like a spit, which the word also means, or a 

 bar ; that a handful made a drachme (Spaxpdl) ', and that the form was 

 afterwards changed from an oblong to a round shape, but that though 

 struck round, like other money, it continued to retain the ancient 

 name. Others say that the obolus was originally so called from being 

 stamped with the figure of a skewer or spit, or other sharp-pointed 

 instrument. 



The Greeks had an herni-obo'lion (TIIUU>&I\IOV) , or semiobolus, and a 

 tri6bolon (Tpui0o\or), or silver coin of three oboli, which was the 

 common pay of the Dicaste! ; the pay originally having been two oboli. 

 Two oboli were placed in the mouth of a dead person, in order to 

 enable him to pay for his passage over Styx. According to Luciau, 

 Charon's demand was only one obelus. (Aristoph., ' Frogs,' 141 ; Lucian, 

 ' CatapL,' i, p. 643.) 



According to Suidas (o/3o\<fs), the Athenian obolua contained six 

 chain (XAKOI)> an< l * ne chaku* contained seven lepta (Aorrci). Other 

 authorities say that the oboliu contained eight chalci. [NUMISMATICS.] 

 OBSERVANTS, or OBSERVANTINS. [FRANCISCANS.] 

 OBSERVATION AND EXPERIMENT. The first of these terms 

 includes a portion of the second, inasmuch as every experiment 

 is made with a view of observing the result. But experiment 

 signifies more than observation, implying a disposition of means 

 of observation which it is in the power of the experimenter to make 

 for himself, and which he actually did make for himself. If, for 

 example, a person who observed the attraction of the magnet for the 

 first tune, dubious of the residence of the attracting power, were to 

 more the magnet to another place, that he might see whether the 

 attracted body would still move towards it, he would make an experi- 

 ment. But if his magnet were the sun and the attracted body the 

 earth, he could only wait the proper times for observing the motion of 

 the latter with respect to the former, in order to establish the 

 attraction. Thus astronomy, geology, meteorology, natural history, 

 Ac., arc sciences of observation (that is, of nothing but observation); 

 while mechanics, optics, electricity, Ac., are sciences of experiment. 

 In one sense geology and meteorology are partly sciences of experiment, 

 since portions of the material subject-matters of these sciences may be 

 submitted to preconcerted tests. It would, however, be more proper 

 to consider mineralogy and aero-mechanics as the experimental sciences 

 connected with these, than to class them as mixed sciences. 



To give an account of experiment would require us to explain the 

 methods of every science which proceeds upon it : to give a detailed 

 account of observation, we should need the description of all the means 

 or instruments by which our senses are assisted in the examination of 

 phenomena. We shall here confine ourselves to a short sketch of the 

 errors which render observations discordant, and which make a final 

 process of combination necessary in every case in which we cannot 

 command results which agree with each other so well that the difference 

 between them is imperceptible to the senses. 



Everything which is called observation is of two kinds ; in the first 

 a simple individual fact is noted, in the second a magnitude is 

 measured. The results of the first species are the proper subjects of 

 inductive reasoning only ; the results of the second, of inductive and 

 mathematical reasoning, either or both. Individually, the first kind of 

 observations are not necessarily subject to error; thus a zoologist 

 observing the structure of a new animal might in every instance 

 correctly note the resemblances which exist between it and other 

 iniiirils, and might refer it to its proper class in a manner which 

 jentnries of succeeding observation would not induce naturalists to 

 disturb. Collectively, however, wrong inferences might be drawn 

 from facts ; thus results of classification which are true of all animals 

 tnown up to one moment, and are therefore inferred to be always 

 ;rue, may be disturbed in the next moment by the discovery of a 

 new specimen. 



Observations of the mathematical character are of necessity erro- 



