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TRANSACTIONS OF THE SECTIONS. 107 
of its excess of water. This hot water passes through a cylindrical chamber round 
the feed-water, so as to heat it on entering. The apparatus is simple, and is stated 
to have worked perfectly well. 
Experiments on the Tubular Bridge proposed by Mr. Stephenson for cross- 
ing the Menai Straits. By W. FAIRBAIRN. 
The experiments undertaken to ascertain the best form of 
bridge for carrying the Chester and Holyhead Railway actoss 
the Menai Straits have led to valuable and important results, 
They have put us in possession of facts which will greatly in- 
crease our knowledge of the properties of a material whose 
powers of combination were but imperfectly understood ; for, 
exclusive of the rapidly increasing use of wrought iron in the 
construction of ships, boilers and other vessels, its application 
to bridges of the tubular form is perfectly novel, and originated 
with Mr. Robert Stephenson. Experiments of the most con- 
clusive character were those made upon a model tube of a large 
scale, containing nearly all the elements of the proposed bridge, 
and the various conditions with regard to form and construction 
which had been developed by the previous inquiries. At first 
it occurred to Mr. Fairbairn that the strongest form would be 
that wherein the top and bottom consisted of a series of pipes, 
with riveted plates on their upper and lower sides. This form 
of top would possess great rigidity, and is well-adapted to re- 
sist the crushing forces to which it is subjected ; and the bot- 
tom section appeared equally powerful to resist tension. Mr. 
Fairbairn is inclined to think that this is the strongest form 
that can be devised ; but practical difficulties present them- 
selves in its construction, as an easy access to the different 
parts for the purposes of painting, repairs, &c. is absolutely 
necessary. The scale of the model tube is exactly one-sixth of 
® the bridge across one of the spans of the Straits, 450 feet* ; 
it is also one-sixth of the depth, one-sixth the width, and, as 
near as possible, one-sixth the thickness of the plates. - With 
these proportions and form, the experiments proceeded as fol- 
lows :—In each of the experiments the weights were laid on 
about a ton at atime; and the deflection was carefully taken, 
as well as the defects of elasticity after the load was removed. 
Rectangular model tube, 80 ft. long, 4 ft. 6 in. deep, 2 ft. 
8 in. wide, and 75 ft. between the supports.— Thickness of the 
plates: bottom,:156in.; sides, 099 in.; Ex ancepandTRANsVERSE 
top, -147.—Sectional area of tne bot- Sperron, ehawine: a 
.Q: . T10) 
tm, Gin, andthe weight the tube stoop 
First experiment. Breaking weight, 
79,578 lbs. = 35} tons.— Ultimate de- 
flection,4:375 inches.— Permanent set, 
or defects of elasticity, with a weight of 
67,842 lbs., :792inch.—With the above 
weight, 352 tons, the bottom was torn 
asunder direct across the solid plates at 
a distance of 2 feet from the centre of 
the shackle from which the load was 
suspended. One of the principal ob- 
jects of this inquiry was to determine 
the ratio or proportion between the top 
and bottom sides of the tube. Taking 
the experiment immediately preceding, it was found that the area of the top to that of 
{S 
boro 
SEE [1 gL 
Elevation, showing a side view of the Tuler, the supports at the ends, and the weight W in the middle, 
* The span has since been increased to 462 feet. 
