MAN 



MAN 



the bulb sealed again, without any sen- 

 sible alteration in its capacity. The air 

 was confined by means of a column* of 

 quicksilver, long or short, and with the 

 buib downwards or upwards, according 

 to the nature of the proposed experi- 

 ment. Here it must be observed, (hat, 

 from the adhesion of the quicksilver to 

 the tube, the instrument will not act truly, 

 except it be in a vertical position ; and 

 even then it is necessary to give it a small 

 degree of motion, to bring the quicksilver 

 into its true place, where it will remain in 

 equilibrio, between the exterior pressure 

 of the atmosphere on one side, and the 

 interior elastic force of the confined air on 

 the other. Pounded ice and water were 

 used to fix a freezing point ori the tube ; 

 and by means of salt and ice, the air 

 was further condensed, generally four, 

 and sometimes five or six degrees below 

 zero. The thermometer and manometer 

 were then placed in a tin vessel among 

 water, which was brought into violent 

 ebullition ; where, having remained a 

 sufficient time, and motion being given 

 to the manometer, a boiling point was 

 marked thereon. After this the fire was 

 removed, and the gradual descents of 

 the piece of quicksilver, corresponding 

 to every twenty degrees of temperature 

 in the thermometer, were successively 

 marked on a deal rod applied to the 

 manometer. It is to be observed, that 

 both instruments, while in the water, were 

 in circumstances perfectly similar; that 

 is to say, the ball and bulb were at the 

 bottom of the vessel. In order to be 

 certain that no air had escaped by the 

 side of the quicksilver during the ope- 

 ration, the manometer was frequently 

 placed a second time in melting ice. If 

 \hd barometer had not altered between 

 the beginning and end of the experiment, 

 the quicksilver always became stationary 

 at or near the first mark. If any sudden 

 change had taken place in the weight of 

 the atmosphere during that interval, the 

 same was noted, and allowance made for 

 it in afterwards proportioning the spaces. 

 Long tubes, with bores truly cylindrical, 

 or of any uniform figure, are scarcely 

 ever met with. Such, however, lis were 

 used in these experiments, generally 

 tapered in a pretty regular manner from 

 one end to the other. When the bulb 

 was downwards, and the tube narrowed 

 that way, the column of quicksilver con- 

 fining the air, lengthened in the lower 

 half "of the scale, and augmented the 

 pressure above the mean. In the upper 



half, the column being shortened, the 

 pressure was diminished below the mean. 

 In this case, the observed spaces both 

 ways from the centre were diminished in 

 the inverse ratio of the heights of the ba- 

 rometer at each space, compared with its 

 mean height. If the bore widened to- 

 wards the bulb when downwards, the 

 observed spaces, each way from the cen- 

 tre, were augmented in the same in- 

 verse ratio ; but in the experiments on air 

 less dense than the atmosphere, the bulb 

 being upwards, the same equation was ap- 

 plied with contrary signs; and if any ex- 

 traordinary irregularity took place in the 

 tube, the corresponding spaces were pro- 

 portioned both ways from that point, whe- 

 ther high or low, that answered to the 

 mean. The observed and equated ma- 

 nomctrical spaces being thus laid down 

 on the pasteboard containing the mea- 

 sures of the tube; the 212 of the ther- 

 mometer, in exact proportion to the sec- 

 tions of the bore, were constructed along- 

 side of them : hence the coincidences with 

 each other were easily seen ; and the num- 

 ber of thermometrical degrees answering 

 to each manometrical space, readily 

 transferred into a table prepared for the 

 purpose." 



MANOR, was a district of ground held 

 by lords or great personages, who kt pt in 

 their own hands so much land as was ne- 

 cessary for the use of their families, which, 

 were called demesne lands, being occu- 

 pied by the lord, or dwiinus manerii f 

 and his servants. The other lands they 

 distributed among their tenants, which, 

 the tenants held under various services. 

 The residue of the manor being unculti- 

 vated, was termed the lord's waste, and 

 served for common of all pasture to the 

 lord and his tenants. All manors exist- 

 ing at this day must have existed as early 

 as King Edward I., and must have a Court 

 Baron. 



MANTELETS, in the art of war, a 

 kind of moveable parapets, made of planks 

 about three inches thick, nailed one over 

 another, to the height of almost six feet, 

 generally cased with tin, and set upon 

 little wheels, so that in a siege they may 

 be driven before the pioneers, and serve 

 as blinds to shelter them from the ene- 

 my's small shot. 



MANTICORA, in natural history, a 

 genus of insects of the order Coleoptera : 

 antennae filiform, the joints cylindrical ; 

 four feelers, filiform ; thorax rounded be- 

 fore, emarginate behind ; head project- 

 ing ; mandibles exserted ; shells united 



