TRANSACTIONS OF THE SECTIONS. 177 
atmosphere which receives the shock or pulsation. But if the water completely 
cover the sirene so as to be an inch or more above the revolving disc, then it is the 
water in the cistern which receives the shock or pulsation. 
The pressure of the water flowing from the reservoir causes the disc to revolve 
under water, and the small streams of water which are forced through the holes 
pierced in the box are cut off in their transit by the movement of the disc, until the 
holes in the disc correspond to those in the box, when the water again rushes through 
and is again stopped, thus keeping up a continuance of regular alternations. The 
slight shocks or pulsations thus created in the water produce musical tones of sin- 
gular purity, which become even purer and more and more sustained as the water 
flows into the cistern. It is also remarkable, that the gravest tones thus produced 
under water are far more readily appreciated, that is, recognised as musical, than 
tones produced by a similar number of vibrations in the atmosphere. 
On a Wrought Iron Tubular Crane, designed by Witt1AM ἙΑΙΆΒΑΙΕΝ, 
ΟΕ. F.R.S. (Communicated by Sir Davin Brewster, K.H., D.C.L., 
F.RS. c.) 
The author presented a plan, side view, and transverse section of the tubular cranes 
which he had designed, and which were now in process of construction for the Keyham 
Dockyards, near Devonport. 
These structures exhibit additional examples of the extension of the tubular system, 
and appear to indicate the numerous advantages which may yet be derived from a 
judicious combination of wrought iron plates, and a careful distribution of the ma- 
terial in those constructions which require security, rigidity and strength. 
Drawings of this new principle of crane having been submitted to the Admiralty, 
six cranes were ordered for the new docks, each of them to sweep a circle of 65 feet 
diameter, and to lift 12 tons to a height of 30 feet from the ground. The projection 
or radius of the jib is therefore 32 feet 6 inches from the centre of the stem, and its 
height 30 feet above the working platform. It is entirely composed of wrought iron 
plates firmly riveted together, and so arranged that the upper side is particularly 
well adapted to resist tension, and the under or concave side, which embodies the 
cellular construction, to resist compression. The form is correctly that of the pro- 
longed vertebrz of the bird from which this useful machine for raising weights takes 
its name; it is truly the neck of the crane, tapering from the point of the jib, where 
it is 2 feet deep by 18 inches wide, to the level of the ground, where it is 5 feet deep 
and 3 feet 6 inches wide. From this point it again tapers to a depth of 18 feet under 
the surface, where it terminates in a cast iron shoe, which forms the toe on which 
the crane revolves. The lower or concave side, which is calculated to resist com- 
pression, consists of plates forming three cells and varying in thickness in the ratio 
of the strain; and on the other hand, the convex or top side, which has to bear the 
pull or tension due to the suspended weight, is formed of long plates connected to- 
gether by the system of “ chain riveting,”’ which Mr. Fairbairn first applied in the 
great tubular bridges in Wales. The sides are of uniform thickness throughout, 
the joints being covered with T-iron intervening, and externally with strips or co- 
vering plates 44 inches wide. This arrangement of the parts and distribution of the 
materials constitute the principal elements of strength in the crane. The form of 
the jib, and the point at which the load is suspended, are probably not the most fa- 
vourable for resisting pressure. It nevertheless exhibits great powers of resistance, 
and its form as well as the position may safely be considered as a curved hollow 
beam, having one end (A) immoveably fixed, the force being applied to the other 
end (C). Viewing it in this light the strengths are easily determined ; and taking 
the ‘experiments herein recorded, we may deduce from the formula W= aa that it 
would require a load of 63 tons to break the crane. With 20 tons the ultimate de- 
flection was 3°97—-°64, permanent set=3°33 inches, the deflection of the jib due to 
a load of 20 tons. The following experiments were made at Keyham Docks on the 
8th and 9th of November last. 
1850. N 
