quite thoroughly, and therefore be of special value.

We might say that in perspective, the lines that run back, and away from the observer, appear to converge instead of appearing parallel, as they actually are.

This is illustrated by a straight line of railway tracks. We all know that if we look along a long stretch of track, the rails appear to converge, and if the distance is great enough, they seem finally to run together.

To be actually correct in showing the work of Fig. 151, the lines of pipe A-B and K-L, instead of being parallel, should be somewhat closer together from B to K than from A to L, but in mechanical perspective, as we may call the work that we are now considering, this principle is

not usually given any consideration.

Very often on such work as shown in Fig. 151 the work as far as we have carried it, is shown in perspective, while the radiators, and all other work above the connections in the cellar, the work would show plain, just as we have hitherto shown it.

In bringing this book to a close with the present chapter we would say that we have endeavored to eliminate as far as possible all technical matters connected with the subject, trying as far as possible to express and explain the ideas to be conveyed in as straightforward and plain wording as possible, for it has been our aim to make the book equally as valuable to the apprentice boy as to the well informed master.