SONS IN' J'UAWING: 



105 



bo directed towards p a ; but ono end beinj? raised from e to d, 



thy whole plane of tlm roof becomeft inclined, conaoqacntly thu 

 vanwhhih' point is raised according to the angle of inrliiuitinn . 

 than f d bvinx detenuim-il, cnntimn! it until it cut 

 dioular Uiio drawn from tlu point of eight, r 8, which will bo at 



Tig. 33 



improve, the hand by practice will Boon become able to carry 

 i <tit with facility all that the mind and eye require. 



We call perspective a portion of the grammar of Art, which 

 assist* as to draw correctly, as the grammar of a language help* 

 us to speak and write correctly ; and, without a grammar, it 



V P. Then, as the opposite side, a b, is, in reality, parallel to c d, 

 a, b must have the same vanishing point ; and all inclined lines of 

 the slates would, if produced, meet at the same point, namely, v P. 

 We regret that at this stage wo cannot give a geometrical proof 

 of this fact, because we fear to confuse the mind of a beginner , 

 with too many rules; but we propose to give him this proof j 



would be as hopeless to succeed in the ono aa it would be in 

 the other. 



Our readers will begin to aee the importance of having a 

 vanishing point, by the help of which we are enabled to draw 

 parallel retiring lines, both horizontal and inclined, accurately. 

 The eye of the draughtsman may be very correct, but he must 



Fij.34 



V P 



hereafter. He must, in copying this example, mark the distance 

 from e to d in the usual manner, draw c d, and carry his pencil 

 on to the perpendicular from p 8; the vanishing point, v P, 

 will then be a guide for the remaining inclined Hues. The eye, 

 in determining the positions and proportions of lines, is very 

 deceptive ; many have recourse to' measuring, in order to ensure 

 a correct outline. We beg the pupil not to measure ; the 

 understanding and the eye must bo educated; and, as these 



not f)is^n.in to use a help which is not only true in principle, 

 but a ready and decisive way of setting at rest every doubt 

 and uncertainty relating to the treatment of these lines, which 

 without vanishing points would bo very difficult to determine. 

 In Fig. 34, the lid of the box to the right inclines downward 

 that is, the upper edge is nearest us consequently, the V P of 

 the lid is below the line of sight ; the lid of the cellar retiree 

 upwards, having its v P above the lino of sight. 



