The Correspondence of Thomas Jefferson
By Subject
PAINE, THOMAS / BRIDGE DESIGN
I will begin with the subject of your bridge, in which I feel myself
interested; and it is with great pleasure that I learn, by your favor
of the 16th, that the execution of the arch of experiment exceeds your
expectations. In your former letter, you mention, that instead of
arranging your tubes and bolts as ordinates to the cord of the arch,
you had reverted to your first idea, of arranging them in the
direction of the radii. I am sure it will gain, both in beauty and
strength. It is true that the divergence of those radii recurs as a
difficulty, in getting the rails on upon the bolts; but I thought this
fully removed by the answer you first gave me, when I suggested that
difficulty, to wit, that you should place the rails first, and drive
the bolts through them, and not, as I had imagined, place the bolts
first, and put the rails on them. I must doubt whether what you now
suggest, will be as good as your first idea; to wit, to have every
rail split into two pieces longitudinally, so that there shall be but
the halves of the holes in each, and then to clamp the two halves
together. The solidity of this method cannot be equal to that of the
solid rail, and it increases the suspicions part of the whole machine,
which, in a first experiment, ought to be rendered as few as possible.
But of all this, the practical iron men are much better judges than we
theorists.
to Thomas Paine, 23 December 1788
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