TRANSACTIONS OF THE SECTIONS. 195 
about 42 ewt. of very combustible materials, such as tar barrels, &c. 
A hose thirty-four feet long, two and a half inches in diametez, ex- 
tended from the boiler of the engine to the cabin, and when the fire 
had been sufficiently kindled, so that the panes of glass in the windows 
of the cabin began to crack by the heat, the steam was let in, and the 
doors of the cabin shut. The fire was extinguished in about four 
minutes. Several trials were made, and all with like success. On 
another trial, a metal pipe of a greater diameter than the hose was con- 
nected with the steam-boiler, and extended into the cabin. <A small 
square hatch was cut in the deck immediately above the cabin, and 
through this opening were lowered down into the cabin two moveable 
grates, each containing a blazing fire, well kindled, and about 1 ewt. of 
coals. The hatch on the deck and cabin doors were then shut, and the 
steam let in, and in fifteen minutes the small hatch was opened, and 
one of the grates hoisted up, when the whole mass of coal and cinders, 
which had before formed a powerful fire, were found to be completely 
extinguished. This experiment was repeated twice with equal success. 
On Timber Bridges of a large size, in special reference to Railways. 
By Mr. Vicno.es. 
Mr. Vignoles took a rapid view of the history of timber bridges, 
tracing their first erection in Germany, then through the United States 
of America, and back to Great Britain. He also described the differ- 
ence between the principles of large bridges constructed with baulks 
and half-baulks, and of timber arches formed of layers of plank laid 
over each other, and fastened securely together, and with felt or other 
means, to make the joints and beds wholly impervious to water. Mr. 
Vignoles stated, that the first bridge on this principle in Great Britain 
had been erected at some place in Scotland, by an ingenious mechanic 
of that country, whose name he regretted not to be able to state. This 
was many years since. The principle had been also made known, par- 
ticularly of late years, by the timber viaducts erected under the direc- 
tion of Messrs. Green and Son, of Newcastle-on-Tyne, who had built 
several, and had designed more; and Mr. Nicholas Wood, of Killing- 
worth, was at this time erecting, for the Duke of Buccleugh, a timber 
viaduct, of great height, and with large openings. Mr. Vignoles then 
explained the peculiar applicability of timber bridges or viaducts to 
the passage of deep ravines, so often met with in hilly and mountain- 
ous districts, illustrating his remarks by diagrams. Instances had 
occurred and might occur, where the whole of a line of railway, other- 
wise highly desirable, would have to be abandoned, unless some ceco- 
nomical construction were devised to surmount the difficulty: and 
here the timber viaduct would most advantageously be introduced, 
since many feet additional height in the level of the railway would add 
but little to the expense. In reference to the expense, he stated, that it 
was chiefly when extraordinary height and either one arch of great span 
were required, or where a series of arches, of large openings, were 
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