ERRAT A.

93.

Page 18. line 24. from the foot, omitted (margin) a 5.1,

3. from the top, for AC is read AG is 136.

12. from the foot, for tirangle read triangle 196.

15. from the foot, for ; read : 196.

13. from the foot, for HBC. And read HBC, and 233 31. from the top, for propofitions, read propofition, 235. - 14. from the foot, for fides read fide 237

2. from the top, for any angle read an angle 237. 27. from the top, for DGE read DGF 241. 25. from the foot, for of P.4. read by P. 4. 242. 22. from the foot, for a circle read the circle 247. 12. from the top, for ET. (margin) read P.T. 266. 11. from the top, for AE read AF 277. 16.& 43. from the top, for Proctus read Proclus 299. 17. from the top, for altogether. read all together.

326. 4. from the foot, for 32d read 2. Cor. 15. Besides these, in the 4th line of the Note to PROB. IX. in p. 320. there is ADE, instead of ADB, and Pl. I. Fig. 16. is omitted in the margin opposite to PROB. X.; and in p. 325. in the first line of the last column of the Table, there is 13, instead of 18.

a

A

Point has situation, but not magnitude.

See Notes II. A line is length without breadth.

III.
The extremities of a line are points.

IV.
A straight line is that which lies evenly between its extreme

points.

a

A superficies is that which hath only length and breadth.

VI.
The extremities of a superficies are lines.

VII.
A plane superficies is that in which any two points being taken,
the straight line between them lies wholly in that super ficies.

VIII. Omitted.

IX.
A plane rectilineal angle is the inclination of two straight lines

to one another, which meet together, but are not in the same
straight line.

B

N. B.

:

6

· N. B. When several angles are at one point B, any one of them is expreffed by three letters, of which the letter that • is at the vertex of the angle, that is, at the point in which • the straight lines that contain the angle meet one another, is

put between the other two letters, and one of these two is * somewhere upon one of those straight lines, and the other

upon the other line: Thus, the angle which is contained by . the straight lines AB, CB is named the angle ABC, or CB.1; " that which is contained by AB, DB is named the angle ABD,

or DBA ; and that which is contained by DB, CB is called • the angle DBC, or CBD; but, if there be only one angle at

a point, it may be expressed by a letter placed at that point ;
as the angle at E.'

X.
When a straight line standing on ano-

ther straight line makes the adjacent
angles equal to one another, each of
the angles is called a right angle ;
and the straight line which stands
on the other is called a perpendicular
to it,

XI.
An obtuse angle is that which is greater than a right angle.

IL

XII.
An acute angle is that which is less than a right angle.

XIII. Omitted.

XIV.
A figure is that which is inclosed by one or more boundaries.

XV.

Book. T.

XV.
A circle is a plane figure contained by

one line, which is called the cir-
cumference, and is such that all
straight lines drawn from a certain
point within the figure to the cir-
cumference, are equal to one ano-

ther:

XVI.
And this point is called the centre of the circle,

Definition A.
Any straight line drawn from the center to the circumference of
a circle, is called a Radius.

XVII. A diameter of a circle is a straight line drawn through the centre, and terminated both ways by the circumference.

XVIII. A semicircle is the figure contained by a diameter and the part of the circumference cut off by the diameter.

XIX. Omitted.

XX.
Rectilineal figures are those which are contained by straight
lines.

XXI.
Trilateral figures, or triangles, by three straight lines.

XXII.
Quadrilateral, by four straight lines,

XXIII. Multilateral figures, or polygons, by more than four straight lines.

XXIV,
Of three-sided figures, an equilateral triangle is that which has
three equal fides.

XXV.
An Isosceles triangle, is that which has only two sides equal.

A A A

XXVI.
A scalene triangle, is that which has three unequal fides.

B 2

XXVII.

Воок І.

XXVII.
V A right angled triangle, is that which has a right angle.

XXVIII
An obtuse angled triangle, is that which has an obtuse angle.

AAA ^

XXIX.
An acute angled triangle, is that which has three acute angles.

XXX.
Of four-sided figures, a square is that which has all its fides

equal, and all its angles right angles.

XXXI.
An oblong, is that which has all its angles right angles, but has
not all its fides equal.

XXXII.
A rhombus, is that which has all its fides equal, byt its angles

are not right angles.

XXXIII.
A rhomboid, is that which has its opposite sides equal to one

another, but all its fides are not equal, nor its angles right
angles.

XXXIV.
All other four-sided figures, besides these, are called Trapeziums.

Xxxv.
Parallel straight lines, are such as are in