TRANSACTIONS OF THE SECTIONS. 109 
The ultimate deflexion of the former tube was about 22 in., and that of the latter 
about 3 in. To ascertain the power of such a tube to bear a side strain—as from 
the action of the wind—the smaller tube above, after being well-repaired, was laid 
on its side, and broken, from a mean of two experiments, with 15:2 tons. Hence 
its Jateral strength was 34 of its vertical nearly ; and in a narrower tube it would be 
considerably less. A number of experiments were made to determine the resistance 
of plates of wrought iron to a force of compression ; and from these considerable in- 
formation has been obtained with respect to the laws of their resistance to flexure or 
buckling. The following table contains the weights, external dimensions, and weights 
of greatest resistance of some of the tubes 10 feet long, which were subjected to 
a force of compression :— 
CYLINDRICAL TUBE. 
Weight of Tube. Exiemial Diameter of Wegus ct Srovteat 
Ibs. OZ. inches, Ibs, 
47 10 2:34 31,828 
45 15 2:99 37,356 
LA Ae 4:05 47,212 
64 4 4:06 49,900 
RECTANGULAR TUBE. ‘ 
43 142 41x41 19,646 
65 8 85x41 23,289 
82 0 81x41 43,673 
OP suk 8:0 x 8:0 27,545 
The rectangular tubes above are all of plates 3th of aninch thick, They were all 
simple rectangles or squares, except the last but one, which had a Givision in it, 
making it into two squares. The proposed tubular bridge has undergone altera- 
tions in consequence of Mr. Hodgkinson's experiments and recommendations :— 
Ist. In the thickness of the side to enable it better to resist the action of the wind. 
2nd. In the top being made straight, instead of curved, to: allow the escape of the 
steam. 3rd. In reducing the rectangular cells at the tcp. In this last instance, 
however, since rectangular tubes are weaker than square ones to resist compression, 
and these much weaker than cylindrical tubes, Mr. Hodgkinson hopes the latter will 
be substituted for the former; as it would, according to the preceding experiments, 
effect a saving of one-fourth of the metal in the top, leaving the strength the same, 
This matter is of the more consequence, as the weight of the tubular bridge will bear 
so large a proportion to the breaking weight. 
Mr. Clarke, the resident engineer of the proposed Menai Bridge, read a statement 
of the principles on which the model tubes for the tubular bridges, on the Holyhead 
Railway, should be increased to larger dimensions. 
On the Law which governs the Resistance to Motion of Railway Trains at 
High Velocities. By J. Scort Russert, M.A. F.RS.B. 
Having on former occasions communicated the results of experimental researches 
concerning the resistance experienced by floating bodies moving along the surface of 
water at high velocities, I have thought it not an inappropriate sequel to communicate 
the general result of a long series of experiments, made partly by committees of this 
Association, and partly by myself. The subject of the resistance which requires to 
be overcome in order to give motion to trains at high velocities has been matter of 
great uncertainty, some dispute, and the cause of several grave errors in practical 
engineering. Some six years ago a committee of the Association was appointed to 
make experiments on this subject, and these experiments were at the time a valuable 
addition to our knowledge. They showed that the resistance at such velocities as 36 
| - miles an hour was much greater than had been supposed—at least double, The 
