COxM 



COM 



COMPOUND interest. See INTE- 

 REST. 



COMPOUND motion, that affected by the 

 concurring action of several different 

 powers. Thus, if one power act in the 

 direction of, and with a force pi'oportion- 

 al to the end of a parallelogram, and ano- 

 ther act in the direction of, and with a 

 force proportional to its side, the com- 

 pound motion will be in the direction of, 

 and proportional to, the diagonal of the 

 said parallelogram. 



COMPOUND numbers, those which may 

 be divided by some other number besides 

 unity, without leaving any remainder: 

 such are, 18, 20, &c. the first being mea- 

 sured by the numbers 2, 6, or 9 : and the 

 second by the numbers 2, 4, 5, 10. 



COMPRESS, in surgery, a bolster of 

 soft linen cloth, folded in several doubles, 

 frequently applied to cover a plaster, in 

 order not only to preserve the part from 

 the external air, but also the better to 

 retain the dressing. See SURGERY. 



COMPRESSION, the act of pressing 

 or squeezing some matter, so as to set 

 its parts nearer to each other, and make 

 it possess less space. 



Water was, during a very long period, 

 considered as a fluid perfectly unelastic : 

 that is, unyielding, or incompressible ; 

 and this opinion was corroborated by an 

 experiment of the Academy del Cimento 

 in Italy. About a century and a half ago, 

 the members of that academy endeavour- 

 ed to ascertain whether water was capa- 

 ble of being compressed in any degree. 

 For this purpose they filled a hollow 

 metallic sphere witk that fluid, and stop- 

 ped the aperture very accurately. This 

 ball then was pressed in a proper ma- 

 chine, but no contraction could be ob- 

 served ; nor, indeed, was the apparatus 

 capable of manifesting small degrees of 

 compression. Hence they concluded that 

 water was not capable of compression. 

 This opinion prevailed until the year 

 1761, when the ingenious Mr. Canton 

 discovered the compressibility of water, 

 and of other liquids, which he immedi- 

 ately made known to the Royal Society. 

 He took a glass tube, having a ball at 

 one end, filled the ball and part of the 

 tube with water, which he had deprived 

 of air as much as it was in his power ; 

 then placed the glass thus filled under 

 the receiver of an air-pump; and on ex- 

 hausting the receiver, which removed 

 the pressure of the atmosphere from 

 over the water and the glass vessel 

 which contained it, in consequenee of 

 which the water rose a little way into 



the tube, viz. expanded itself. He then 

 placed the apparatus under the receiver 

 of a condensing engine, and on forcing 

 the air into it, which increased the pres- 

 sure upon the water, a diminution of bulk 

 evidently took place; the water descend- 

 ing a little way within the tube. "In 

 this manner," Mr. Canton says, " I have 

 found by repeated trials, when the heat 

 of the air has been about 50, and the 

 mercury at a mean height in the barome- 

 ter, that the water will expand and rise 

 in the tube by removing the weight of 

 the atmosphere, one part in 21740, and 

 will be as much compressed under the 

 weight of an additional atmosphere. 

 Therefore the compression of water by 

 twice the weight of the atmosphere is 

 one part in 10870." " Water has the re- 

 markable property of being more com- 

 pressible in winter than in summer, 

 which is contrary to what I have observ- 

 ed both in spirits of wine and oil of 

 olives." By the same means, and in the 

 same circumstances, Mr. Canton ascer- 

 tained the property of being compressed 

 in some other fluids, and the results are 

 as in the following table : 



Millionth part. 

 Compression of spirit of wine - 66 



oil of olives - - - 48 



. - - - - rain water - ... 46 



- - - - - sea water 40 



mercury 3 



COMPTONIA, in botany, so called in 

 honour of Henry Compton, Lord Bishop 

 of London, a genus of the Monoecia Tri- 

 andria class and order. Essential cha- 

 racter : male ament. calyx two-leaved; 

 corolla none ; anthers two-parted. Fe- 

 male ament. calyx six-leaved ; corolla 

 none ; styles two : nut. ovate. There is 

 but one species, viz. C. asplenifolia, fern- 

 leaved Comptonia, a native of North 

 America. It is an astringent, and is in 

 considerable estimation as a remedy for 

 fluxes. It is brought to the Philadelphia 

 market abundantly for this purpose. 



COMPUTATION of a planet's motion. 

 See PLANET. 



COMPUTATION, in law, is used in re- 

 spect of the true account or construction 

 of time, so understood as that neither par- 

 ty to an agreement, &c. may do wrong 

 to the other; and that the determination 

 of time be not left at large, or taken 

 otherwise than according to the judg- 

 ment and intention of law. 



If a lease is ingrossed, bearing date Ja- 

 nuary 1, 1808, to have and to hold for 



