TRANSACTIONS OF THE SECTIONS. 
163 
On the Limit of Weight which may safely he laid on a Pile driven into the 
Ground. By Professor Stevelly, LL.D Belfast. 
The force which resists the penetration of a pile may, under very peculiar circum- 
^ces, diminish as the pile is driven downwards ; but for the most part it increases, 
“J generally towards the last strokes it receives from the ram the increase is very 
raaidcrable. A simple test for this was pointed out by the author, vu. after the 
keen driven as deep as intended, letting the ram descend on it from a less 
•rot than the previous stroke, and carefully comparing the two distances it has 
»ui thus driven. If the resistance increase, then the actual load the pile can bear 
' nut be less than what it would be if the resistance were strictly uniform which 
experienced as it penetrated. This last force admits of a very simple calcu- 
,which, therefore, a most certain limit to the load ur dead weight that 
•is without its sinking further may he obtained. The author 
K! nt ™ out the two dynamic principles on which the calculation was founded : 
3 ? ovin S mass * W, strikes another W at rest with the velocity v, then 
velocity, after impact, 
lWt W+W' 
^itanrp . raov ' n 8 with the velocity v', is stopped by a uniformly acting 
!, vt . «tat resistance can be compared with the weight that gives the velocity 
•e.u'^re of th* i ^ principle that the force or resistance is proportional to the 
frrtc act .. e velocit y gained or destroyed, divided by the space through which the 
^braic rtpaiPlf 01 lake ** awa y- The following practical rule is, then, a simple 
«tn in tong • w°v ^ rontl t ^ ese two principles, bet W denote the weight of the 
wid decimal’ r tae w ! 3 'S* lt; o1 ’ the pile in tons and decimals ; h, the height in feet 
^‘roala of ! /°? ^ich the ram is let fall un the final stroke ; d, the depth in 
of bad (in t nn the last stroke causes the pile to penetrate. L, the limit 
tons) that may with safety be laid on the pile, shall then be,— 
L = W. ( ■ W . ft) ; 
, [w + w> U 
» » ana a, can all be had by actual weighing and measurement. 
Gn an improved Printing Machine. By J. Stather. 
Mr, J m 
w hich means tfi' a commu nication "On an Iron Floating Graving Dock 
e 8 “'P 8 to be repaired are raised by caissons of a peculiar shape. 
^ ^ e port of p 
^ x Perimen/^f e> i meniS on ^ ie F r * ct ‘ on of Discs in Water and on the 
o oe made on Centrifugal Pumps. By J. Thornton. 
11* 
