SCIENTIFIC SUMMARY. 
209 
MECHANICAL SCIENCE. 
SiqjpoHing Power of Piles . — An extremely interesting communication on 
tlie supporting power of wooden piles, and on the mode of sinking cylinder 
foundations, has been sent by Mr. McAlpine, C.E. of New York, to the 
I Institute of Civil Engineers. In forming the government graving dock at 
Brooklyn, some 6,539 piles were sunk to an average depth of 32 feet. The 
j piles were on the average 7 in. diameter at the smaller, and 14 in. at the 
larger end. Most of them were driven by a piling engine, the head of 
I which weighed 2,200 lbs. and fell 30 feet. The distance through which the 
pile was driven varied uniformly from 8 in. at the beginning to nothing at 
the end of the operation. With a Nasmyth piling engine, the head of 
which weighed three tons, the fall being 3 ft., the strokes 60 to 80 per 
minute, the same piles were driven 35 ft. in 7 minutes, whilst with the 
other machines they required an hour or more to drive them the same dis- 
tance. Experiments were made on the supporting power of the piles driven 
by the ordinary piling engines to the point at which they ceased to give 
under the blows of the one ton ram. It was found that they required 125 
tons of statical load to cause them to move. Mr. McAlpine has given a 
formula founded on this result, which, however, appears to be of too em- 
pirical a character to be of much service. The mode of sinking cylinder 
foundations, similar to those employed at Rochester Bridge and at the 
Thames bridges, is also described, and Mr. McAlpine states that he found 
the ultimate supporting power due to friction of these cylinders, when sunk 
20 to 30 ft. in moderately fine gravel, to be half a ton per square foot of 
external surface. According to M.'Haertner, how’ever, the supporting power 
of such cylinders does not exceed 300 lbs. per square foot of external surface. 
. Removing Mountains . — Under this title the great cutting on the proposed 
ship canal in Western Canada is described in Engineering. This cutting is 
8| miles long, with an average depth of 80 ft., a maximum depth of 198 ft., 
and will require the removal of 36,000,000 cubic yards of material, or 
18 times as much as the two mile cutting of the London and North Western 
Railway at Tring. At the rate of half a million cubic yards annually, 
which is about as much as has been excavated in this country, this cutting 
would require 72 years for its completion. Recourse is therefore proposed 
to the steam excavator, capable of removing 1000 yards per day. In the 
paper from which we quote it is suggested to turn the site of the cutting 
into a reservoir or lake, and dredge out the material, aa^he cheapest and 
most rapid means of effecting its removal. The steam excavator or steam 
shovelling machine, although nearly unknown in this country, has been 
extensively used in America, where manual labour is costly and scarce. It 
is capable of removing about 1000 to 1200 cubic yards in the twenty-four 
hours. 
Steel Rails . — In December, a steel rail on the Charing Cross Bridge broke 
during the passage of a train, without however causing any mishap. The 
rail had been rolled in 1864, and was a flat-footed rail weighing 70 lbs. to 
the yard. A piece of the top table of the rail, 20 in. long, was detached by 
a fracture extending downwards and longitudinally to the end of the rail. 
