1875.] Engineering. 397 
by night inspectors to detect where a waste of water occurred, and, on the 
discovery of any such instance, measures are adopted to dete& the cause and 
provide such remedy as might be necessary. ‘The result of the trials thus far 
has been to show that with proper precautionary measures a constant service 
may be introduced so as to secure a lower consumption than under the inter- 
mittent system. 
Ships.—The recent action taken in Parliament by Mr. Plimsoll has led to 
greater attention being given to the construction of shipping, and the extent 
to which this has taken place is shown in the nature of the papers read before 
the Institute of Naval Archite&s. Foremost amongst these is one by Mr. W. 
Froude on the “Rolling of Ships.” This is a most important question as 
affecting the stability of vessels, but the difficulty in its proper determination 
consists in the theoretical nature of the necessary calculations, and the 
difficulty in ascertaining the actual resistance to oscillation presented under 
varying circumstances. In the absence of this resistance every ship of 
ordinary form would infallibly be overset the first time she encountered co- 
periodic waves. This is a very serious fact, and Mr. Froude has undoubtedly 
done good service in endeavouring to frame rules for the solution of so difficult 
a problem. 
The superiority of steel over iron for shipbuilding has been ably explained 
by Mr. N. Barnaby, who showed that the French are in advance of this 
country in the adoption of the superior metal for that purpose. The principal 
care to be taken in its use is to avoid hammering the metal as much as 
possible, and to bend it to the necessary curves by means of pressure, so as 
to afford as little injury as possible during the process of construction. The 
chief advantage of steel is that it is homogeneous, and free from all lami- 
nations and blistering, and the recent improvements in its manufacture 
enable it to be turned out in sufficient quantities for the purpose in view. 
An interesting paper by Mr. A. Sedgwick Woolley on “Spar Torpedo 
Warfare ” was another contribution to the proceedings of the Institution of 
Naval Architects. In this paper the history of torpedo warfare is traced from 
the year 1775, and one Captain David Bushnell, of Conne@ticut, is said to 
have been the originator of the system, which, however, did not arrive at any 
really practical use until during the Civil War in America, when it was 
brought largely into use by the Southern States against the war vessels of 
their opponents. The results of experience gained up to the present time 
seems to be that the torpedo should explode only by actual conta& with the 
vessel against which it is directed, because unless it is a@tually in contaé with 
the side of a vessel, there is a great chance of the explosion failing to blow it 
in, since it will always take the line of least resistance. The plan of firing at 
will has the disadvantage of being left entirely to the discretion of the 
operator, who, in the darkness of night, under cover of which these attempts 
have to be made, may easily miscalculate the distance he is from a ship, and 
so fire his torpedo too soon. Some fast torpedo launches have recently been 
constructed by Messrs. Thorneycroft and Co., from the Swedish, Norwegian, 
and Danish Governments. 
Within the last quarter there has been launched the twin-screw ironclad 
Alexandra, for the British Navy, which is justly described as the finest and 
most powerful broadside ironclad in the world. The following are her 
principal dimensions:—Length between perpendiculars, 225 ft.; extreme 
breadth, 63 ft. 8 in.; depth in hold, 18 ft. 7} in.; tonnage, 6049 tons; indi- 
cated horse-power, 8000; and speed, 14 knots. The water-line of the 
Alexandra is protected by a belt 12 inches in thickness amidships, which tapers 
off towards the ends. The Alexandra is a central battery ship, and needs no 
bow or stern batteries to give her end-on fire; she has two gun-decks with 
end-on fire from both, and the batteries are armoured with 8 in. and 6 in. 
armour. The upper battery of this vessel consists of two 25-ton and two 
18-ton guns, whilst in the lower battery are eight 18-ton guns. 
Another vessel of special interest, which has recently been added to our 
commercial fleet, is the Bessemer steamer, designed primarily for cross 
