FART IV. 



AGRICULTURE. 



205 



SECT. I. OF THE GENERAL CAUSES OF THE FAILURE OF 

 EMBANKMENTS ALREADY MADE. 



The general causes of failure are two : the first concerns the 

 form of the embankment ; and the second the materials with, 

 which it is constructed. 



1. With respect to form. — Embankments are generally made 

 too narrow at the base, in proportion to their height; by which- 

 means, the side next the sea is too upright (as is represented in 

 Plate X. fig. %.) Hence, it is unable, in high tides, to with- 

 stand the weight of the sea ; which, it must be remembered,, 

 presses laterally as well as downwards, Another very bad. 

 consequence of this form is^ that the tides, in ebbing or flow- 

 ing^ act a longer time on one place^than if the slope were more 

 gradual ; and, consequently, they have a much greater ten- 

 dency to break or damage the surface of the bank. Most of 

 the embankments that have been constructed in England are 

 of this form, more or less varied, and the materials generally of 

 earth or turf. Bays, or creeks, are the most favourable situa- 

 tions for this kind : there, if they endure until the sea leaves 

 sand or mud against them, so as to form a gradual slope next 



