IN C 



392 



IND 



to the angle of refection. Thus ACE = 



BCF and ECG = FCO. HcrealsoGC 



Is the axis, EC the line, and C the point, 



G 



C 



of incidence ; sometimes termed the in- 

 cident axis line, or point. 



INCI'SOR, Lat. from incido, to cut ; a cut- 

 ting tooth. The four front teeth of both 

 jaws are called incisors. 



INCLINATION , from in and clino, to lean. 

 A term employed by mathematicians to 

 denote the mutual approach, tendency, 

 or leaning of two lines, planes or sur- 

 faces, towards each other, so as to make 

 an angle at the point of their contact of 

 greater or less magnitude. The angle of 

 inclination is otherwise called the angle 

 of incidence (see INCIDENCE). The inclin- 

 ation of the earth's axis is the angle which 

 it makes with the plane of the ecliptic. 

 The inclination of a planet is the angle 

 comprehended between the ecliptic and 

 the plane of the planet in its orbit. For 

 inclination of magnetic needle (see DIPPING 

 NEEDLE). 



INCLI'SED PLANE. In mechanics, & plane 

 wh'-ch forms with a horizontal plane some 



angle less than a right angle. It is one of 

 the simple mechanical powers, and its pro- 

 portion is Power : Weight : : Height of 

 plane : Length of plane, or, P : W : : H L. 

 Whence P = and W = 



INCLI'NERS. a name for inclined or in- 

 clining dials, or such as are drawn on 

 planes not perpendicular to the horizon. 



IXCI.U'SA, a family of Mollusca: order 

 Acephala Testacea. The mantle is open at 

 the anterior extremity, or near the mid- 

 dle only, for the passage of the foot, and 

 extended from the other end into a double 

 tube which projects from the shell. Nearly 

 all of them live buried in sand, stones, 

 ooze, or wood. 



INCLU'SI or RKCLC'SI, Lat. shut up. A 

 class of religious persons who lived in 

 cells, under the obligation of not leaving 

 them except in cases of extreme necessity. 



IKCOMBUS'TIBLE, not combustible. Ap- 

 Vl-ed in chemistry to bodies neither capa- 

 t.c i.-t supporting combustion nor of un- 



dergoing combustion. Only cnc rock 

 substance is at present known, namely, 

 nitrogen. Cotton and linen fabrics arc 

 said to be incombustible when they are 

 rendered incapable of taking fire, or of 

 burning with flame, by being imbued 

 with some preparation, as alum, sal- 

 ammoniac, &c. ; and incombustible cloth 

 and paper have been manufactured from 

 the fibrous mineral called amianthus. 



INCOMMENSURABLE, not commensurable. 

 /. lines are such as have no common mea- 

 sure. Thus the diagonal and side of a 

 square are incommensurable, being to 

 each other as \/ 2 to * I - numbers are 

 such as are prime to each other, or have 

 no integral common measure greater 

 than 1. 



INCOMPA'TIBLES. In chemistry, such sub- 

 stances as cannot exist together in solu- 

 tion without mutual decomposition. 



INCOMPLETE, Lat. incompletus, not com- 

 plete. Applied to flowers which want 

 either the cup or blossom. 



IN'CREMENT, Lat. incrementum, increase. 

 Used in fluxions to designate the finite 

 increase of a variable quantity. Dr. Brook 

 Taylor, to whom we are indebted for the 

 Doctrine of Increments or Finite Differ- 

 ences, denoted his increments by a dot 

 under the variable quantity: thus the 

 increment of was denoted by * ; others 

 have employed an accent, thus z' or f. 

 M. Nicole employed another letter, as * ; 

 but Euler who seems to have given a per- 

 manent form to this branch of analysis, 

 employs the character & ; thus A x = in- 

 crement of r. In rhetoric, a species of 

 climax rising from the lowest to the 

 highest. 



iNCRrsTA'riox (Fr.). In architecture and 

 sculpture, work fixed with cement into 

 notches made to receive it. 



INCUNAB'CI.*, Lat. cradle. A term ap- 

 plied to books printed before the year 1500. 



IN'CCS, Lat. <mrtl. The largest bone of 

 the tympanum of the ear, thus named 

 from its shape. 



INDECLI'NABLE, not dcolimable. Applied 

 to words (nouns), not varied by termina- 

 tions. 



IN DEFEASIBLE. In law, that cannot be 

 defeated. 



INDEFINITE. In logic, an indefinite pro- 

 position is one which has for its subject a 

 common term, without any indication 

 whether it is distributed or not. In bo- 

 tany, when stamens are above twenty in 

 number, or in other cases when their 

 number cannot be readily counted. 



INDEHIS'CENT, Lat. in and dthisco. to trape. 

 Applied to a fruit, of which the pericar- 

 pium continues closed when the fruic it 

 ripe. 



INDEN'TCRE, a writing containing a 

 contract, as of apprenticeship. Indpn- 



