comprehended by more than two, there is an infinite procession. For there are certain figures contained by three and four and succeeding circumferences. Thus, if three circles touch each other, they will intercept a certain trilateral space; but if four, one terminated by four circumferences, and in like manner, by a successive progression. But of those contained by right lines, some are comprehended by three, others by four, and others by a multitude of lines. For neither is space comprehended by two right-lines, nor much more by one right-line. Hence, every space comprehended by one boundary, or by two, is either mixt or circular. And it is mixt in a twofold manner, either because the mixt lines comprehend it, as the space intercepted by the cissoidal line; or because it is contained by lines dissimilar in species, as the apsis: since mingling is twofold, either by apposition or confusion. Every right-lined figure, therefore, is either trilateral, or quadrilateral, or gradually multilateral; but every trilateral, or quadrilateral, or multilateral figure, is not right-lined; since so great a number of sides is also produced from circumferences. And thus much concerning the division of plane figures. But we have already asserted[177], that rectitude of progression is both a symbol of motion and infinity, and that it is peculiar to the generative co-ordinations of the gods, and to the producers of difference, and to the authors of mutation and motion. Right-lined figures, therefore, are peculiar to these gods, who are the principles of the prolific energy of the whole progression of forms. On which account, generation also, was principally adorned by these figures, and is allotted its essence from these, so far as it subsists in continual motion and mutation without end. DEFINITION XXIV. Of three-sided FIGURES: an EQUILATERAL TRIANGLE is that which has three equal Sides. DEFINITION XXV. An ISOSCELES TRIANGLE, is that which has only two Sides equal. DEFINITION XXVI. A SCALENE TRIANGLE, is that which has three unequal Sides. DEFINITION XXVII. A RIGHT-ANGLED TRIANGLE is that which has a Right Angle. DEFINITION XXVIII. An OBTUSE-ANGLED TRIANGLE is that which has an Obtuse Angle. DEFINITION XXIX. An ACUTE-ANGLED TRIANGLE is that which has three Acute Angles.