TRANSACTIONS OF THE SECTIONS. 177 
mass was, the less was the weight of the ek tse upon it, and the better 
adapted as a foundation to resist its pressure. He then described the system he had 
pursued in the construction of four bridges over the Thames, and also of the pier 
at Greenock. He considered it important that the foundation of each pier should 
be one undivided structure; that it should not be broken into separate parts, as it 
was in cases where cylinders were used; and that, besides the resistance due to the 
horizontal area of the foundation, it should embrace the additional resistance 
afforded by the friction due to the vertical surface of the pile; and this, short of 
founding on rock itself, would present the most solid resisting mass that could be 
found. The system afforded great facility and rapidity of construction, and its 
2g alam to harbours of refuge was a subject of great interest and importance at 
the present time, both for expedition in completing the works and for economy. 
New Plan for Hanging Dock-Gates. By R. A. Pracocx, C.L., of Jersey. 
The works of docks and harbours must necessarily be strong and durable, and 
therefore expensive; but any new methods of construction which are sufficiently 
durable and convenient, and by which expense is considerably reduced, are so much 
gained (he exhibited models of gates, showing how the mortices and tenons were 
immovable). Shipping having gradually but largely increased in dimensions during 
the last twenty years, it became necessary to provide wider and deeper water- 
ways to docks, and consequently dock-gates of greater height and length. Rollers 
for the outer ends of the gates to travel upon, by means of tramways at the bottom 
of the water, were apparently thought indispensable. These tramways, being below 
the level of the sill of the lock, necessarily became more or less covered with mud, 
sand, &c., and were, as a matter of fact, so difficult to open and shut with suitable 
expedition, as to render necessary the very valuable but at the same time very 
costly hydraulic apparatus now in use. The question is, Can gates be so constructed 
as to carry themselves without rollers, and so as to save a large portion of their 
first cost, and the whole of the heavy first cost and annual expense of hydraulic 
power? After mentioning a number of inconveniences incident to the present 
system of dock-gates, he went on to say—To prevent all these inconveniences, 
why not treat the dock-gate like an ordinary field-gate >—make all its parts strong 
in proportion to its weight, which, in the present case, is about 45 tons; make it 
carry itself, and so dispense with rollers and tramways. He then proceeded to de- 
scribe, first, the girder and its fastenings, which are to carry our dock-gate as a 
gate-post carries its field-gate, and then the suspended gate from the girder. He 
then remarked that this is clearly an advantage over gates of the usual system, 
where the pivot is at the bottom, and inaccessible on account of the weight of the 
gate, and also on account of the mud and the water: the bottom of the heel-post 
fits into a strong cast-iron shoe. He then referred to the construction of the gate, 
so as to secure sufficient rapidity and enable the gate to carry itself without the 
use of rollers ; and having described the minor details of the gate, went on to show 
the immobility of the tenons and mortices. He stated that four lockmen could 
work two pairs of these gates at a cost for wages of only about £200 per annum, 
and the heavy cost of hydraulic power is got rid of altogether. 
Description of the Large Gyroscope used by Sir William Armstrong in his 
investigations on Rifled Projectiles. By Professor Wiri1am Por, F.R.S. 
At an early period of these investigations Sir William perceived that the motion 
of a rifle ball had considerable analogy with that of the spinner of the gyroscope ; 
but, as the instruments usually sold under that name were imperfect, he contrived 
a much larger and better form of the machine, which enabled him to study more 
satisfactorily the nature of its motion, and more particularly to ascertain accurately 
the numerical value of the various elements entering into its calculation. Mr. 
Pole had, at the time referred to, been requested by Sir William Armstrong to 
undertake the theoretical investigation of the action of the machine. He pro- 
duced and worked the instrument, and gave a general exposition of its principles, 
and of the formule referring to it; and he finally showed its application to explain 
some facts in gunnery. 
1863, = 12 
