TRANSACTIONS OF THE SECTIONS. 173 
thus be adopted will lessen the difficulty of launching; and there will then be less 
confusion by these boats being unencumbered, more promptly loaded and despatched 
from the ship’s side—a place of danger in bad weather, with the passengers more 
divided. There will then be less danger of rushing to the best or first boat, when 
every one on board is satisfied that there is room enough in the boats for all, and 
that all are equally good. 
The boats are so constructed that any number will fit one within the other, as 
internal projections are dispensed with and thwarts folded. Flat, half-round, or 
angle iron or iron plates are used to impart the necessary strength. Although the 
inventor prefers to form the boat with two bows, they may yet be made with a 
bow and stern. These boats are, moreover, admirably adapted for pontoon pur- 
poses, as the displacement of each boat is equal to that of a pontoon ; and half-a- 
dozen boats, with the displacement of six poutoons, may be packed in the space 
of one pontoon. 
Remarks on Armour-Plating for Ships. By Captain Dovetsas Gauron, FRS. 
After referrmg to the experiments on the Warrior target, the author remarked : 
The most severe test to which any target has been subjected at Shoeburyness is 
far less severe than the ordeal which ships would have to withstand in defending 
the entrance of or in forcing a passage into a harbour. At the trial of the Warrior 
target, already referred to, the nature and extent of the test to which it was sub- 
jected were as follows :—Twenty-nine rounds in all struck the target, embracing 
a total weight of 3336 Ibs. of metal, propelled by 400 Ibs. of powder, and repre- 
senting an amount of work done in foot-pounds of 62,570,000; of this total, how- 
ever, 32,392,000 go to the credit of shell and solid shot at low velocities, which 
are held to be almost innocuous against such targets as the Warrior. Of the 
thirteen rounds of solid shot at high velocities, four only were 68-pounders (and 
one of these is said to have missed the target), representing work done to the ex- 
tent of 10,260,000 foot-pounds—about one-sixth of the total work; and, if one 
round missed, as alleged, one-eighth. Thus, three out of the twenty-nine rounds 
go to the credit of the old 68-pounder, which is said to be the most effective gun 
in the service against iron plates. Of the twenty-nine rounds not more than five 
or six were fired in salvo, and yet the plates were deeply indented, buckled, and 
badly fractured, and many of the fastening-bolts were broken; so that, had the 
target been part of the side of a ship rolling on the sea, the plates would probably 
have fallen off in consequence of the destruction of the fastenings. But the strain 
in such a test as this is far less than that from a well-concentrated broadside, such 
as the crew of every French ship is regularly exercised to give. The arrangement 
required for the armour-plating of a ship is a strong front plate, in which deflection 
under blows shall be prevented, but which shall have some cushion behind to pre- 
vent the full concussion of the blow being communicated to the side of the ship. 
The best form to distribute material in a beam, so as to prevent deflection, is to 
obtain depth ; hence, in tubular girders, the top and bottom flanges are separated 
by a comparatively light web. Without exactly comparing the effects of the blow 
of a shot to the weight of a beam, it is apparent that as the best form in which to 
place the material to resist shot is that which will allow of the smallest yielding at 
the point of impact, it follows that, after reserving a sufficient face of metal for the 
front plate, the remainder should be placed in that shape which is resorted to for 
obtaining stiffness in beams. The authorthen described the target invented by 
Mr, Chalmers. 
On Air-Engines and an Air-compressing Apparatus. 
By J. Jamuson, Close Engine- Works, Newcastle-on-Tyne. 
The author pointed out that in the steam-engine not more than one-seventh of 
the total consumption of heat was utilized, and then proceeded to enumerate the 
causes of the non-success of the air-engines which have hitherto appeared, re- 
ferring to two as types of the whole. In the first he showed that, in addition to 
the heat required to work the engine, there was a consumption of heat in the hot 
chambers of the generators, resulting only in the development of heat in the cold 
chambers, which actually resisted the action of the engine ; that this absorption and 
