76 Papers connected with the construction No. 81. J 



, 5th. The forces that will be exerted upon the Pier, at all seasons. 



6th. The part where the projected work will be exposed to the greatest 

 risk of injury, and the precautions to be taken against their being receiv- 

 ed. 



7th. The principle of the structure proposd to-be erected, the materials 

 to be' employed, their strength, stability, and thence their capability of 

 resisting the force exerted upon the Pier, their durability and the ex- 

 pedients to be resorted to, to preserve the structure from a rapid decay. 



The bottom of the Sea at Madras is a stratum of sand, white and 

 grey, perfectly pure, and consequently of the best character for receiving 

 and firmly retaining piles ; the sand may have a less or greater thickness 

 above the stratum of clay, upon which it rests, without any inconveniency 

 for the hold of the piles ; for if this thickness of the sand is such that the 

 piles can be wholly driven in, the depth attained will be so much greater, 

 while if the clay is to be met, before the piles are sufficiently driven, this 

 inferior stratum being harder, the depth attained will be less, but on 

 account of the greater hardness of the soil, the hold of the piles shall be 

 as great. 



Shifting sands do not exist, but at the mouth of large rivers where 

 a violent current, in its encounter with the sea, meets with a great 

 resistance producing eddie? which moving the bottom of the sea, throw 

 off the sands on one side and another, and thus form sandy banks that 

 shift their position according to the direction of the currents. No such 

 thing existing at Madras, we may conclude a priori that there are no 

 shifting sands. The theory^ in this circumstance, agrees with the facts. 

 The divers interrogated by Capt. Biden, have declared that, beyond two 

 fathoms, they have never observed any shifting of the sea's bottom. It 

 is on this side only that there is a sort of shifting bank, so that differences 

 may have been found in sounding where it exists, and attributed to shift- 

 ing sands while they were owing to tire shifting of the bank, according to 

 its being at a less or greater distance from the shore. It results from the 

 soundings taken last November, that, from the beach to a distance of 80 

 fathoms where the depth of water is 9 feet, the slope of the sea's bottom 

 is nearly regular, that, at a distance of 90 fathoms, the depth is 14 feet, 

 which gives a difference of 5 feet for a length of 10 fathoms only, while, 

 for a length of 60 fathoms from this point, the depth of water at 150 

 fathoms from the shore being 23 feet, the difference is but 9 feet. 

 Thus the bottom of the sea, within these limits is composed of two 



