landscape, one running right through the group of spears.  The use of the diagonal is another remarkable thing in the lines of this picture.  If you place a ruler on the slanting line of the flag behind the horse’s head to the right, you find it is exactly parallel to a diagonal drawn from the top right-hand corner to the lower left-hand corner.  Another line practically parallel to this diagonal is the line of the sword belonging to the figure offering the key, the feeling of which is continued in the hand and key of this same figure.  It may be noted also that the back right leg of the horse in the front is parallel to the other diagonal, the under side of it being actually on the diagonal and thus brought into relation with the bounding lines of the picture.  And all these lines, without the artifice being too apparent, give that well-knit, dignified look so in harmony with the nature of the subject.

[Sidenote:  Curved Lines]

Curved lines have not the moral integrity of straight lines.  Theirs is not so much to minister to the expression of the sublime as to woo us to the beauteous joys of the senses.  They hold the secrets of charm.  But without the steadying power of straight lines and flatnesses, curves get out of hand and lose their power.  In architecture the rococo style is an example of this excess.  While all expressions of exuberant life and energy, of charm and grace depend on curved lines for their effect, yet in their most refined and beautiful expression they err on the side of the square forms rather than the circle.  When the uncontrolled use of curves approaching the circle and volute are indulged in, unrestrained by the steadying influence of any straight lines, the effect is gross.  The finest curves are full of restraint, and excessive curvature is a thing to be avoided in good drawing.  We recognise this integrity of straight lines when we say anybody is “an upright man” or is “quite straight,” wishing to convey the impression of moral worth.

Rubens was a painter who gloried in the unrestrained expression of the zeal to live and drink deeply of life, and glorious as much of his work is, and wonderful as it all is, the excessive use of curves and rounded forms in his later work robs it of much of its power and offends us by its grossness.  His best work is full of squarer drawing and planes.

#Always be on the look out for straightnesses in curved forms and for planes in your modelling.#

Let us take our simplest form of composition again, a stretch of sea and sky, and apply curved lines where we formerly had straight lines.  You will see how the lines at A, page 164 [Transcribers Note:  Diagram XIV], although but slightly curved, express some energy, where the straight lines of our former diagram expressed repose, and then how in B and C the increasing curvature of the lines increases the energy expressed, until in D, where the lines sweep round in one vigorous swirl, a perfect hurricane is expressed.  This last, is roughly the rhythmic basis of Turner’s “Hannibal Crossing the Alps” in the Turner Gallery.