SCIENTIFIC SUMMARY. 
537 
mately some spheres were burst at 1,650 lbs. per square inch, the 
safe working pressure of the boiler being therefore nearly 300 lbs. 
per square inch. One remarkable feature of this boiler is an entire free- 
dom from corrosion and incrustation. As to its evaporative efficiency, 
experiments show an evaporation of 442*7 cubic feet of water by 38 cwt. 
of coal, or 6£ cubic feet of water per pound of fuel. Making allowance 
for the loss in heating the water, boiler, and brickwork at starting, Mr. 
Colburn estimates the average evaporation at 8 cubic feet of water per 
pound of fuel. 
The “ Great Eastern .” — Dr. W. Fairbairn has made a report to some 
gentlemen interested in the great ship favourable to the removal of the 
paddle-engines as an expedient for reducing the cost of working. He 
estimates the money saved on three voyages per annum to Calcutta at 
£20,000, the speed being reduced from 14 to 10| knots per hour. It is to 
be hoped, however, that means will be found to make this noble vessel 
answer commercially without the sacrifice of such distinctive features as the 
combination of paddles and screw and the resulting high speed at sea. 
Armstrong and Whitworth Guns. — Nothing official has yet been made 
known as to the results of these trials, which have been prosecuted 
vigorously. It is reported, however, that whilst the Whitworth 12 Pr. gun 
exhibited great lateral accuracy, the deviation of 10 shots at 1,600 yards 
being only 5 inches, the vertical deviation was considerable, a wall 8|- feet 
high being hit directly only seven times out of fifteen. The Armstrong is 
said to have done better in this respect. Each 12 Pr. gun has now fired 
2,500 rounds, or three times the number required to destroy the old brass 
field-piece. At 4,000 yards Mr. Whitworth has the advantage in range by 
400 yards. 
Institute of Naval Architects. — This association has held its session under 
the presidency of Sir J. Pakington with great success, iron-plated vessels 
of war affording the chief subject of discussion. Mr. E. J. Reed narrated 
a series of experiments confirming previous theoretical calculations, and 
proving that the centre of gravity of armour-plated ships is lower 
than that of the old wooden sliips-of-the-line ; and consequently, so far 
from being unsteady from top-weight, as has been alleged, they are more 
stable than the ships they replace. Mr. Cunningham described a mode of 
working heavy guns on shipboard by shafting connected with a steam- 
engine. The shafting has drums, round which a turn or two is taken by 
the slack rope of each of the ordinary gun tackles. When the slack of 
any rope is hauled on, it bites on the drum which accordingly works the gun, 
but when the end of the rope is let loose it slips. Captain Scott advocated 
wooden facing to armour-plates instead of backing, a plan which has been 
found to be successful when opposed to solid shot alone, but which is 
apparently open to the insuperable objection that the facing may be blown 
off in sheets by shell, leaving the iron exposed. Mr. J. Scott Russell read 
a paper on the present state of the questions at issue between modern 
guns and armour-plated vessels. The resistance of plates to shot he 
stated as follows : 4^-inch plates cannot be penetrated by cast-iron 
spherical shot from service guns ; nor 5^-inch plates by 68 lbs. steel shot ; 
nor 6-inch plates by 9-inch steel shot. No plate has been found to resist the 
projectile of the 300-pounder. Mr. Barnes demonstrated a mode of ascer- 
