0.5

1 cm

pidlure i and is the just distance at which the speclator

should survey the picture. The question is, in what

part of the picture the eye (I] wall perceive the point

A? To determine this, the point A is united to the

bottom (or ground line) of the picture, by a line parallel

to I C ; where it intersects the picture, at the ground

line, is termed its feat on the picture ; the seat on the

picture being united by a line to the center C (i. e. its

vanishing point) It follows, that in sorne part of this

line will be the representation of A : the exact place

is found, by uniting I and A, which gives a for the

true siliation of A on the picture to the eye at I.

No. III. Is exactly the same example diversified by

a point on each side A, which worked by the former

process, gives for x A. 2. the representation 1 a. 2.

No. IV. Instead of the points being placed on each

side to form aline (as in No. III.) in this example, the

line is formed forward. The representation is equally

found by obtaining its seat on the picture, and uniting-it

to its vanishing point; then drawing A I. B I. to deter-

mine its length.

No, V. Is a curious problem, shewdng the imperfec-

tion of the art of perspeclive geometrically considered.

Every thing (landing as in No. IV. it appears by this

figure, that the representation a b (of A B) may likewise

be the representation of any line in any diredlion whose

extremes will give the points a b. Thus Ai. A 2. or A 3

may equally appear to I to be A B. This being evident,

it mav be asked, how then do we determine with re-

spect to the real forms of objects ? The rcason is

partly because by perpetual use the mind acquires the

habit

should survey the picture. The question is, in what

part of the picture the eye (I] wall perceive the point

A? To determine this, the point A is united to the

bottom (or ground line) of the picture, by a line parallel

to I C ; where it intersects the picture, at the ground

line, is termed its feat on the picture ; the seat on the

picture being united by a line to the center C (i. e. its

vanishing point) It follows, that in sorne part of this

line will be the representation of A : the exact place

is found, by uniting I and A, which gives a for the

true siliation of A on the picture to the eye at I.

No. III. Is exactly the same example diversified by

a point on each side A, which worked by the former

process, gives for x A. 2. the representation 1 a. 2.

No. IV. Instead of the points being placed on each

side to form aline (as in No. III.) in this example, the

line is formed forward. The representation is equally

found by obtaining its seat on the picture, and uniting-it

to its vanishing point; then drawing A I. B I. to deter-

mine its length.

No, V. Is a curious problem, shewdng the imperfec-

tion of the art of perspeclive geometrically considered.

Every thing (landing as in No. IV. it appears by this

figure, that the representation a b (of A B) may likewise

be the representation of any line in any diredlion whose

extremes will give the points a b. Thus Ai. A 2. or A 3

may equally appear to I to be A B. This being evident,

it mav be asked, how then do we determine with re-

spect to the real forms of objects ? The rcason is

partly because by perpetual use the mind acquires the

habit