GEOMETRICAL AND ENGINEERING DRAWING. 81 



the workmen. Then carpentry, which includes the 

 accurate delineation of joints, mortices, wooden staircases, 

 roofs, &c. Last of all I may mention isometric projection, 

 although, in truth, that is nothing more than an example 

 of descriptive geometry. It is, however, quite possible 

 to learn stone-cutting, and one or two other branches, 

 without knowing anything of descriptive geometry. If all 

 these various branches of drawing are thoroughly mastered, 

 it becomes very easy to apply them to any engineering 

 designs. However complicated, their execution is then a 

 mere matter of time and practice, though without some 

 fundamental notion of descriptive geometry, draughtsmen 

 have often to struggle against difficulties of execution, 

 which they could have resolved without any trouble by a 

 little previous study of this most useful subject. 



I shall now proceed briefly to explain a few of the 

 models and instruments before us. There is on the wall a 

 series of diagrams, or rather a small number of the series, 

 which I shall briefly explain. They were published by 

 the French Government for the elementary schools in 

 France, and are more especially used in Paris, where the 

 Freres de la doctrine Chretienne have the charge of the 

 primary schools. "We have here also a series of plaster 

 models, one or two of which are on the table. The dia- 

 grams are divided into two parts : one of them treats of 

 pure geometry, and contains examples of lines perpendicular 

 to and forming angles with each other, polygons, circles, 

 ellipses, and so forth. Next come a few more difficult 

 examples, such as prisms, pyramids, and a few little 

 examples of machines, such as nuts, thumb-screws, &c. 

 Then, lastly, come a few instances of architectural draw- 

 ing. Examples of all of these are given, so as to enable 

 the beginner to understand at once the use of plan, eleva- 

 tion, and section. All that I have referred to is supposed 

 to be taught in one year. In the second year comes this 

 second portion, of which there are but a few examples 

 here. In that year the student is taught first, shading ; 

 and here are some examples, showing the theoretical draw- 

 ing of the shadows of various bodies. Then a selection 

 of stone-cutting, which is a more important subject, and to,, 

 one example I would ask your attention, because we have-, 

 before us a model made from it. The students, as they 



VOL. II. Q 



