® 
Improvement in the Construction of Bridges, §c. 279 
twenty years’ experience in bridges, the patentee feels confident 
of no one fact, in science and practical mechanics, more than 
this, that the wider the spans are adopted, the greater, by far, is 
the strength and durability of this last improvement, when suita- 
bly executed to such width of span, compared with any other 
mode of construction now in use. If, indeed, this were not the 
fact, beyond a doubt, in the mind of the patentee, he certainly 
hot only would not trouble himself with its introduction into 
public use, but would promptly admit that this, or any other mode 
hot possessed of such principles, would neither be entitled to the 
credit of a ‘general system,” or be possessed of any other ad- 
vantages worthy of public confidence or patronage. 
It has ever been his opinion, even from the firs?, that this mode 
of combining materials, when properly perfected by practical ex- 
perience, was such as not only to possess all the advantages that 
Science could render in its mathematical principles, but also to 
have the immense advantages of the application, in its mechani- 
cal execution, of materials, which may be procured in any 
fart of the country, with the greatest ease, dispatch, and econ- 
omy. 
It is also found, in a long practice of this particular Sanaa 
that the advantages in the mechanical execution, by using light 
timber, combined of sawed planks, and by a disttibuition, there- 
fore, of the strain or weight to be overcome, into such an almost 
innumerable number of nearly equal parts, that the strength of 
any material, even the softest pine, becomes abundantly sufficient 
to sustain its portion of such strain; and the mode, also, of se- 
curing each and every part of the niece without the aid 
of iron, becomes practicable—so amply sufficient as to ensure 
strength, rigidity, and durability, to a degree, most certainly not 
to be even very nearly approached by any other system of com- 
bination and mechanical execution in practice. The great and 
equal distribution of the material, in the sides or trusses of the 
bridge ; the immense number of intersections or crossings of the 
timber, in each truss, which are, each and all of them, thoroughly 
secured by four, three, or two hard wood tree-nails, of two inches 
in diameter, according as each particular intersection may require, 
in the importance of its situation for the purpose of bearing its 
part of the strain ; and, lastly, and by no means the least impor- 
tant, the advantage gained in this mode, which has never been 
