Next draw the end view of the cylinder and steam-chest. Since the cylinder has been given a diameter of 3¼ inches in the side view, of course it must have the same diameter in the end view as shown in Fig. 17.
[Illustration: FIG. 17. AN END VIEW OF A STEAM ENGINE]
By looking again at Fig. 16 you will see that the steam chest is 4½ inches long and that it is 2½ inches high but it is in the end view Fig. 17, that the width of it is shown. The end of the steam chest is shaded with straight parallel evenly spaced lines and the cylinder head is shaded with _concentric circles_, that is with circles equally spaced apart and having the same center.
[Illustration: FIG. 18. A TOP VIEW OF A STEAM ENGINE]
In this and many other cases a side view and an end view give all the outside dimensions needed but sometimes a top view must also be made, and this is shown in Fig. 18.
[Illustration: FIG. 19. A CROSS-SECTION OF A STEAM ENGINE]
While all of these views show the outside of the steam chest and the cylinder they give no hint as to how the inside is made. Suppose you had invented the steam engine of course you would know how the inside should be made and so you make a cross-sectional drawing of the parts as shown at Fig. 19, and then the construction and even the operation of the engine looms up as though you had turned a searchlight on it.
[Illustration: FIG. 20. THE SIDE VALVE SHOWN IN DETAIL]
That is all of it will be clear except perhaps the slide valve and this is where a detailed drawing comes in to show a small part, or a part that is hard to understand by looking at the side, end and top views. The slide valve, see Fig. 20, is drawn in detail and the picture is made large and bold. The slide valve is made of a cast piece of metal hollowed out. It and the completed steam chest and cylinder are both drawn in _perspective_, that is just as the eye would see them if they were actually made of metal. The latter is shown in Fig. 21.
[Illustration: FIG. 21. AN ISOMETRIC PERSPECTIVE DRAWING OF A STEAM ENGINE]
~A Simple Way to Draw in Perspective.--~Did I hear you ask how you can make a drawing in perspective? List and I will tell you the simplest way--a way so that you do it the first time you try.