first detect the law of
ascent in the peaks, but if the height of any one of them were altered,
the general form would instantly be perceived to be less agreeable. Fig.
107 shows that they are disposed within an infinite curve, A _c_, from
which the last crag falls a little to conceal the law, while the
terminal line at the other extremity, A _b_, is a minor echo of the
whole contour.

[Illustration: FIG. 107.]

Sec. 50. I must pause to make one exception to my general statement that
this structure had been entirely ignored. The reader was, perhaps,
surprised by the importance I attached to the fragment of mountain
background by Masaccio, given in Plate +13+ of the third volume. If he
looks back to it now, his surprise will be less. It was a complete
recognition of the laws of the lines of aqueous sculpture, asserted as
Turner's was, in the boldest opposition to the principles of rock
drawing of the time. It presents even smoother and broader masses than
any which I have shown as types of hill form; but it must be remembered
that Masaccio had seen only the softer contours of the Apennine
limestone. I have no memorandum by me of the hill lines near Florence;
but Plate +47+ shows the development of limestone structure, at a spot
which has, I think, the best right to be given as an example of the
Italian hills, the head of the valley of Carrara. The white scar on the
hill side is the principal quarry; and the peaks above deserve
observation, not so much for anything in their forms, as for the
singular barrenness which was noted in the fifteenth chapter of the last
volume (Sec. 8) as too often occurring in the Apennines. Compare this plate
with the previous one. The peak drawn in Plate +46+ rises at least 7500
feet above the sea,--yet is wooded to its top; this Carrara crag not
above 5000,[97]--yet it is wholly barren.

Sec. 51. Masaccio, however, as we saw, was taken away by death before he
could give any one of his thoughts complete expression. Turner was
spared to do _his_ work, in this respect at least, completely. It might
be thought that, having had such adverse influence to struggle with, he
would prevail against it but in part; and, though showing the way to
much that was new, retain of necessity some old prejudices, and leave
his successors to pursue in purer liberty, and with happier power, the
path he had pointed out. But it was not so: he did the work so
completely on the ground which he chose to illustrate,