Illustrations can only be read and comprehended by minds that have been educated in the language they use to convey thought to the mind. To a geometrician, a few lines drawn on a ﬂat surface will express that which can be shown to the novice only by means of blocks and of careful drawings. In this book the language of illustration is one that can be comprehended by all minds: it is the language of form, of visible presences. The student. Can see the lines brought together in actual projection, and can then more readily understand the geometric plan the parts will cover when laid back upon the level surface of the illustration. An elementary work that impresses so forcibly the practical value of the rules it is designed to teach, will interest the student and afford him excellent mental training, without overtasking the mind by mere memorizing.