78 Papers connected ivith the construction No. 81.] 



stand an equal exertion. It consists in wrought iron piles driven at the 

 greatest depth possible, and tied, the ones to the others by braces of the 

 same metal, by the means of cast iron collars wedged upon the piles. Be- 

 ing thus bound together, one of the piles cannot yield without the others 

 yielding at the same time. The effect of this contrivance is that no part 

 of the Pier can yield unless the braces which bind the piles are torn off, the 

 Pier being fixed at one end in a solid masonry work, and, at the other 

 end, at a plat form composed of a great number of piles tied together in 

 such a manner that it is immovable ; it could but slide on the bottom of 

 the sea, if the piles were not driven in ; but, even in this case ; the weight 

 is so great that, on account of the small surface exposed to the force ex- 

 erted upon the Pier, it could not be moved. The Pier having its two ex- 

 tremities firmly fixed and immovable there is no risk of its yielding on 

 one side nor on the other, besides, this effect is so much the less to be 

 feared that the direction of the force exerting itself upon the Pier, being, 

 as has been afore stated, perpendicular to the coast, tends to crush or tear 

 it off rather than to make it yield ; therefore, we must calculate what will 

 be the force exerted, and the resistance opposed by the piles and the braces 

 which bind each row of the Pier to the neighbouring ones. Admitting 

 the most unfavourable circumstances, that is to say, a maximum of force 

 exerted upon the greatest surface possible, and a minimum of intenseness 

 for the resistance, it will be easy to ascertain whether this resistance is 

 sufficient or not. We supposed that the waves will rise to the height of 

 the middle braces of the rows which are 7 feet above the level of the sea ; 

 then the force will be exerted upon it, upon the braces below, the half 

 parts of the cross braces which bind them, and upon the piles, on a length 

 of 1 1 feet. 



The area of one of the braces is 3s?./. 135s?. i. which gives for the 

 four 15s?./. 108s?. i. ; it is for a half part of a cross brace 2s?./. 69s?. i. 

 and for the 4 together, 9s?./. 132s?. the area for a pile, supposing it 

 equal to that of a square inscribed in a circle of the same diameter will be 

 3sq.f. 30s?. i. for a length of eleven feet, and for the 3 piles 9s?./. 9s?. i 

 Thus the whole surface exposed to the shock of the waves will be 33s?./ 

 42s?. v. admitting now thafthe force exerted is the same for the whole 

 height of the waves, though it is not so, it will be, at the rate of 7701bs. 

 for each square foot, 256341bs or 229 cwt. for a surface of 33s?./, 42s?. I 

 This force as we have already stated tends to bend and crush the braces, or 

 tear them off. Let us suppose that the piles will offer no resistance, and 

 calculate only that of the braces which bind them. The area of the trans- 

 verse section of one of the longitudinal braces is 6s?. i. 120s?. /. which 

 gives for the six 41s?. i. It is for the transverse section of the diagonal 



