ISS 



ITT 



2. Of two isoperimetrical triangles, 

 having the same base, whereof two sides 

 of one are equal, and of the other une- 

 qual, that is the greater whose two sides 

 are equal. 



3. Of isoperimetrical figures, whose 

 sides are equal in number, that is the 

 greatest which is equilateral and equian- 

 gular. From hence follows that common 

 problem of making the hedging or walling 

 that will wall in one acre, or even any 

 determinate number of acres, a ; fence 

 or wall in any greater number of acres 

 whatever, b. In order to the solution of 

 this problem, let the greater number, b, 

 be supposed a square ; let x be one side 

 of an oblong, whose area is a : then will 



- be the other side ; and 2 - -f 2 x will 

 x x^ 



be the ambit of the oblong, which must 

 be equal to four times the square root of 



5 ; that is, 2 - + 2 x = 4 </ b. Whence 

 oc 



the value of x may be easily had, and you 

 may make infinite numbers of squares and 

 oblongs that have the same ambit, and 

 yet shall have different given areas. 

 Let v/ b 



xx dx = 



_~ 



Thus if one side of the square be 10, 

 and one side of an oblong be 19, and the 

 other 1 ; then will the ambits of that 

 square and oblong be equal, viz. each 40, 

 and yet the area of the square will be 100, 

 and of the oblong but 19. 



ISOPYRUM, in botany, a genus of the 

 Polyandria Polygynia class and order. 

 Natural order of Multisilique. Ranuncu- 

 laceae, Jussieu. Essential character: calyx 

 none ; petals five ; nectary trifid, tubular ; 

 capsule recurved, many-seeded. There 

 are three species. 



ISOSCELES triangle, in geometry, one 

 that has two equal sides. See GEOMETRY. 



ISSUE, in law, has many significations, 

 sometimes being used for the children be- 

 gotten between a man and his wife ; 

 sometimes for profit growingfrom amerce- 

 ments or fines ; and sometimes for profits 

 of lands or tenements ; sometimes for 

 that point of matter depending in a suit, 

 when, in the course of pleading, the par- 



ties in the case affirm a thing on one side, 

 and deny it on the other, they are then 

 said to be at issue ; all their debates being 

 at last contracted into a single point, 

 which may be determined either in favour 

 of the plaintiff or defendant. 



ISSUES, in surgery, are little ulcers made 

 designedly by the surgeon in various 

 parts of the body, and kept open by the 

 patient for the preservation or recovery 

 of his health. 



ITCH, a cutaneous disease, supposed 

 to be caused by an insect, a species of 

 the genus Acarus, viz. A. scabiei, which, 

 when viewed by a good microscope, is 

 white with reddish legs ; the four hind 

 ones having a long bristle. It is found in 

 the small pellucid vesicles with which 

 the hands and joints of persons infected 

 with the itch are covered. It appears to 

 be not only the cause of the disorder, but 

 the reason why it is so highly infectious. 



ITCHING, an uneasy sensation, which 

 occasions a desire of scratching the place 

 affected. It is frequently a troublesome 

 sensation, but more nearly allied to plea- 

 sure than pain. As pain is supposed to 

 proceed from too great an irritation, so 

 does itching proceed from a slight one. 

 Certain species of itching excites people 

 to many necessary actions, as the excre- 

 tion of the feces and urine ; coughing, 

 sneezing, &c. 



ITEA, in botany, a genus of the Pen- 

 tandria Monogynia class and order. Natu- 

 ral order of Rhododendra, Jussieu. Es- 

 sential character : capsule two-celled, 

 two-valved, many-seeded ; stigma emar- 

 ginate. There are two species, viz. I. 

 virginica. Virginian itea ; and I. cyrilla, 

 entire -leaved itea. These are both shrubs. 

 Linnxus remarks, that the itea virginica 

 has the appearance of the Padus ; that 

 the leaves are petioled and the flowers in 

 terminating racemes. The stigma is head- 

 ed in this species, whereas in the other 

 it is bifid or double ; the former is a native 

 of North America ; the latter of Carolina 

 and Jamaica. 



ITTRIA. This earth was discovered 

 by Gadolin, a Swedish chemist, in a fossil, 

 found at Ytterby, in Sweden, which has 

 since received the name of gadolinite, 

 and in which it is combined with silex 

 and lime. The discovery was confirmed 

 by Ekeberg, Klaproth, and Vauquelin ; 

 and the same earth has been discovered 

 in some other fossils, particularly com- 

 bined with lantalium. In several of its 

 properties ittria resembles glucine, par- 

 ticularly in forming salts of a sweet taste, 

 and in being soluble in carbonate of am- 

 mania ; but it differs entirely in others. 



