Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. There is a common opinion that a quick sketch demands less skill and training than a completed drawing. The truth lies in the opposite direction. For the sketch is an expression, in comparatively few strokes, of many facts to be read between the lines. These remarks should not discourage the beginner, but rather stimulate him to study in such a way that his sketches may become the means of valuable service.