Through his absence and avocations, several sheets went to the press without any assistance, and the rest had the occasional inspection of one or two other friends. If any inaccuracies shall be found in the writing, I shall readily acknowledge them all my own, and am, I confess, under no great concern about them, provided the matter in general may be found useful and answerable in the application of it to truth and nature; in which material points, if the reader shall think fit to rectify any mistakes, it will give me a sensible pleasure, and be doing great honour to the work. ADVERTISEMENT. _For the more easy finding the figures referred to in the two prints belonging to this work, the references are for the most part placed in the margin. Fig._ T p. I _signifies the top of plate_ I. L p. I _the left side_. R p. I _the right side_. B. p. I. _the bottom. And where a figure is referred to in the middle of either print, it is only mark'd thus, fig._ p. I _or fig._ p. II. [Transcriber's note: In this digital edition, these marginal references have been incorporated into the text within square brackets, e.g. [fig. 1 T p. I]. The two prints were not originally bound into the book; they are reproduced in their entirety below. Reproductions of the individual figures have also been incorporated into the text at the appropriate points.] [Illustration: PLATE I] [Illustration: PLATE II] CONTENTS. page PREFACE. iii ADVERTISEMENT. _The plates and figures_. xxii INTRODUCTION. _The use and advantage of considering solid objects as only thin shells composed of lines, like the outer-coat of an onion_. 1 CHAPTER I. _Of FITNESS_, 13 CHAPTER II. _Of VARIETY_, 16 CHAPTER III. _Of UNIFORMITY, REGULARITY, or SYMMETRY_, 18 CHAPTER IV. _Of SIMPLICITY, or DISTINCTNESS_, 21 CHAPTER V. _Of INTRICACY_, 24 CHAPTER VI. _Of QUANTITY_, 29 CHAPTER VII. _Of LINES_, 37 CHAPTER VIII. _Of what sort of parts and how PLEASING FORMS are composed_, 39 CHAPTER IX. _Of COMPOSITIONS with the WAVING LINE_, 48 CHAPTER X. _Of COMPOSITIONS with the SERPENTINE LINE_, 50 CHAPTER XI. _Of PROPORTION_, 67 CHAPTER XII. _Of LIGHT and SHADE, and the manner in which objects are explained to the eye by them_, 93 CHAPTER XIII. _Of COMPOSITION with regard to LIGHT, SHADE, and COLOURS_, 106 CHAPTER XIV. _Of COLOURING_. 113