THE MADRAS HARBOUR. 



63 



If, however, the obstacle is placed below these levels the 

 wave has no effect, and if the obstacle be an upright wall 

 its foundation is as secure as if it were entirely on dry land. 



"What we have to do, therefore, is to ascertain at what 

 depth below water a given material is immoveable under the 

 action of the waves, and take care that that material forms 

 no part of our structure, or of the support of it, above that 

 level. 



Now, simple as this principle seems to be, it has not been 

 applied in practice without much battling with the waves. 

 Notwithstanding a popular belief to the contrary, engineers 

 will not be parties to spending their employers' money unless 

 they clearly see an equivalent ; so the costly practice of 

 building under water by the help of divers was not resorted 

 to till the plan of laying the foundations of the upright wall 

 of masonry at the level of the lowest tides had been fairly 

 tried. But -Neptune would have none of this. Incensed by 

 the invasion of his territory by a huge mass, too heavy for 

 him to remove by direct force, he attacked the looser material 

 at its foot, and round its end, till it was undermined, and then 

 the wall, however well put together, fell to pieces, and the 

 pieces were rolled about by the waves. 



So the engineers conceded 6 feet, and employed divers to 

 prepare the foundation at that depth. But this was not 

 enough. The next moderately heavy sea, perhaps, had no 

 effect upon the work, and delusive hopes of success were 

 raised, but in a few months came one of greater severity, and 

 it became evident that Neptune claimed for his own 6 feet 

 under water. 



Then 12 feet was tried, and it is debateable whether, in 

 very exposed situations, this is sufficient or not. It has proved 

 to be so in some cases of exposure to tremendously heavy seas, 

 but in other cases there are indications to the contrary, 

 But now a new element comes in, If we must employ 



