4H4 



LIFE-PRESERVERS LIGHT. 



end, a large knob, marked " LIFE-BUOY :" this alone 

 is UM-il in tin- iby-tiii)*'. C' lose at hand is anotlier 

 wooden knob, marked ' LOCK," fastened to the end 

 of a line fixed to the trigger of a gun-lock primed 

 with powder, and so arranged that, when the line is 

 pulled, the port-fire is instantly ignited; while, at the 

 same moment, the life-buoy descends, and floats 

 merrily away, blazing like a light-house. The gunner, 

 who has charge of the life-buoy lock, sees it freshly 

 and carefully primed every evening at quarters, of 

 which he makes a report to the captain. In the 

 morning, the priming is taken out, and the lock 

 uncocked. During the night, a man is always sta- 

 tioned at this part of the ship ; and every half hour, 

 when the bell strikes, he calls out " Life-Buoy !" to 

 show that he is awake and at his post, exactly in the 

 same manner as the look-out men abaft, on the beam 

 and forward, call out. " Starboard quarter !" " Star- 

 board gangway!" "Starboard bow!" and so on, 

 completely round the ship, to prove that they are 

 iiot napping. Captain Basil Hall's Fragments of 

 f'oyages; second series. 



LIFE-PRESERVERS. The human body is a little 

 lighter than an equal bulk of water, so that it natur- 

 ally floats in this fluid. The mouth, however, in the 

 case of most men lying motionless in the water, would 

 sink below the surface, if the head were not thrown 

 back by a muscular effort. Many persons who fall 

 into still water, and are unable to swim, might be 

 saved, if they had any presence of mind sufficient to 

 preserve a proper position. The specific levity of 

 the body, in comparison with water, makes it easy 

 to keep the upper part of it considerably elevated 

 above the surface of the water by attaching to the 

 chest some buoyant substance, even though its bulk 

 be not great ; and many contrivances, called life-pre- 

 servers, have been invented with this view. A great 

 portion of them, however, have been found, in prac- 

 tice, of little or no use. One of the latest is the 

 invention of a Mr Scheffer, in England. It consists 

 of a hollow cylinder, formed without a seam, and 

 perfectly air-tight, bent when distended with air and 

 ready for use : or it is what may be termed a cylindri- 

 cal ring, without a seam, and without a break. Of 

 this ring, the external diameter is generally about 

 22 inches, the internal diameter ' about 12, and the 

 diameter of the cylinder about 5L the dimensions vary- 

 ing, of course, by being specially adapted to the size 

 of the person by whom it is designed to be employed. 

 It contains a small stop-cock, to which an ivory pipe 

 is fixed. Through this pipe the air is injected by the 

 mouth, and retained by the stop-cock ; the adjust- 

 ment and inflation only occupying the short space of 

 one minute. When unexpanded, it folds up into a 

 very small compass, so as to be conveyed in the 

 pocket ; and is also very portable, its weight being 

 but twelve ounces. Another life-preserver, invented 

 by a gentleman of Connecticut, America, does not 

 differ essentially from this, except that it is a straight 

 cylinder. It is made of cloth without a seam, and 

 rendered impervious to water by a preparation of 

 caoutchouc; is about two feet, or two and a half feet 

 long, and eight or ten inches in diameter ; is filled 

 like the one first described, and secured to the body 

 by means of straps passing over the shoulders. When 

 empty, it occupies but little room, and may even be 

 worn by a man labouring on the deck of a vessel in 

 danger. He can inflate it in a few moments, when 

 he finds it necessary to trust himself to the waves. 



LIGAMENT, in anatomy ; a strong, compact sub- 

 stance, serving to join two bones together. A liga- 

 ment is more flexible than a cartilage, not easily 

 niptured or torn, and does not yield, or at least yields 

 very little, when pulled. 



LIGATURE, in surgery, is a cord, band, or string; 



or the binding any part of the body with a cord, band, 

 fillet, &c., whether of leather, linen, or any other 

 matter. Ligatures are used to extend or replace 

 bones that are broken or dislocated ; to tie the 

 patients down in lithotomy and amputations ; to tie 

 upon the veins in phlebotomy, on the arteries in 

 amputations, or in large wounds ; to secure the 

 splints that are applied to fractures ; to tie up the 

 processes of the peritoneum, with the spermatic ves- 

 sels, in castration ; and, lastly, in taking off warts or 

 other excrescences by ligature. Ligature is also used 

 to signify a kind of bandage or fillet, tied round the 

 neck, arm, leg, or other part of the bodies of men or 

 beasts, to divert or drive off some disease, accident, &c. 



LIGATURES, among printers, are types consist- 

 ing of two letters or characters joined together ; as 

 ff, fl.fi. The old editions of Greek authors are ex- 

 tremely full of ligatures ; the ligatures of Stephens 

 are by much the most beautiful. 



LIGHT is that which renders objects perceptible 

 to our sense of seeing. It is one of the most interest- 

 ing subjects that fall under the contemplation of the 

 philosopher : at the same time it must be acknow- 

 ledged to be one that is as little understood, and upon 

 which opinions are as much divided, as any of the 

 most abstruse subjects of philosophical inquiry. Some 

 consider light as a fluid per se ; while others consider 

 it merely as a principle, and attribute to it a sort of 

 pression, or vibration propagated from the luminous 

 body through a subtile, ethereal medium. The 

 ancients believed it to be propagated from the sun 

 and other luminous bodies instantaneously ; but the 

 observations of the moderns have shown that this was 

 an erroneous hypothesis, and that light, like any other 

 projectile, employs a certain time in passing from one 

 part of space to another, though the velocity of its 

 motion is truly astonishing, as has been manifested in 

 various ways. And first, from the eclipses of Jupi- 

 ter's satellites ; it was observed by Rcemer, that the 

 eclipses of those satellites happen sometimes sooner 

 and sometimes later than the times given by the tables 

 of them, and that the observation was before or after 

 the computed times, according as the earth was nearer 

 to or farther from Jupiter than the mean distance. 

 Hence it was concluded that this circumstance de- 

 pended on the distance of Jupiter from the earth ; 

 and that, to account for it, we must suppose that the 

 light is fourteen minutes in crossing the earth's orbit. 

 The original observations have received some cor- 

 rections, and it is now found that, when the earth is 

 exactly between Jupiter and the sun, his satellites 

 are seen eclipsed about eight minutes and a quarter 

 sooner than they could be according to the tables ; 

 but when the earth is nearly in the opposite point of 

 its orbit, these eclipses happen about eight minutes 

 and a quarter later than the tables predict them. 

 Hence, then, it is certain that the motion of light is 

 not instantaneous, but that it takes up about 16 

 minutes of time to pass over a space equal to the 

 diameter of the earth's orbit, which is nearly 

 190,000,000 of miles in length, or at the rate of 

 200,000 miles per second a conclusion which, it 

 may be added, is placed beyond doubt, by the aber- 

 ration of the stars discovered by the celebrated doctor 

 Bradley. 



Upon the subject of the materiality of light, doctor 

 Franklin observes, in expressing his dissent from the 

 doctrine that light consists of particles of matter con- 

 tinually driven off from the sun's surface, with such 

 enormous swiftness " Must not the smallest portion 

 conceivable have, with such a motion, a force exceed, 

 ing that of a twenty-four pounder discharged from 

 a cannon? Must not the sun diminish exceedingly 

 by such a waste of matter, and the planets, instead of 

 drawing nearer to him, as some have feared, recede 



