were to be laid together?—I have a specimen of the proposed manner lying in my yard now.

Can you give any account of the manner in which the bars are either laid or joined together ?-We took a number of bars of iron, half an inch square, and composed them into a square piece consisting of thirty-six, that composed a square of three inches, and upon the outside of each of the sides we put a circular piece, so as to form the whole into a round bar or a round cable; these bars were not welded, but laid together; the intention was, to have each half-inch bar of the whole length of the bridge, namely, 1,000 feet; it was proposed, therefore, that as many of the half-inch bars as would be required to make out the 1,000 feet, should be welded together longitudinally, so as to be united into one bar, and the whole laid together as I have described; it was proposed, after the whole were laid together, to envelope the whole with wire twisted round, and fill the interstices with some substance which would render the whole impervious to

water.

Was any experiment tried on the strength of the whole bar so united?-No; I do not suppose there are any means in the kingdom of trying it?

That is to say, you do not apprehend that it would have been possible, by any mechanical apparatus of which we are in possession, to have applied a sufficient weight or force to have broken that bar asunder?—I do not know of any such apparatus.

Are you perfectly satisfied, that by the application of a number of similar cables, the sufficiency of which should be ascertained by experiments, to a bridge of 500 feet water-way, every thing necessary for absolute and entire security may be attained ?—I am quite certain of it.

Do you apprehend that the means of applying such cables

cables are easy to any practical engineer in the present state of the science?-That is giving great latitude; but I should say, in the hands of any prudent and skilful engineer, certainly it is quite practicable and easy.

Mr. Thomas Brunton, called in; and examined.

You are a proprietor of the patent chain and cable manufactory?—I am.

Are you acquainted with any experiments that have been made on the strength of iron?-Yes; we have made many hundred experiments, several for Mr. Telford, at different times.

Where do you reside?-Our manufactory is in the Commercial Road.

Describe the experiments which you have made at Mr. Telford's request, for the purpose of ascertaining the strength of iron?-The machine we have got is a hydrostatic power, which has been examined by a number of the first engineers in the kingdom; and there is, I believe, but one opinion with regard to the accuracy of it; the force we consider it capable of applying is 250 tons; an inch circular bolt of iron will carry on an average from 22 to 24 tons, according to the quality of the iron, but we have seldom or never found it to exceed 24 tons; from the experiments we have made upon larger bolts, we find that they increase in strength; a two-inch bolt, for instance, will carry near upon 100 tons, from 95 to 100 tons, sometimes as high as 103; the difference of a round bolt to a square we consider to be, that a square, the side of which is equal to the diameter of the round, will be about one-fifth stronger; a two-inch bolt is the largest we have drawn asunder.

What is the greatest length of any of the bars you ever

tried?—About two feet six inches was the length of those upon which we have made experiments.

Have you, from experiment or observation, any opinion whatever to give respecting the accuracy of the application of these results to bars of any very considerable length? I should say there could be no difference if the bar was ten times the length, provided the bar was all equally joined.

Are the short bars of which you speak made in those short lengths, or are they parts only of longer bars cut into those lengths?-Cut into those lengths.

May it not then very easily happen, that the defect of which you speak might occur in the shorter bar as well as in the longer one?—On trying the experiment, we in general endeavour to get a piece of iron as sound as possible for the experiment.

Are not those means of ascertaining the soundness of the bar equally applicable to the longer bar as to the shorter ones?-It might be, but still I should apprehend, that there was more danger in the longer than in the shorter bar.

Are not the means of ascertaining it equally applicable? -Certainly.

You rather mean then, that it requires greater care and attention to ascertain the uniform strength of a long bar than of a short one ?-Certainly.

Do you not apprehend, that two bars of iron, with the reasonable care that is to be demanded upon those occasions, may be so welded together, as to be no more liable to separate where they are welded than in any other part; the question, supposing the best iron, and in the most convenient shape, and with every advantage which can be given to it for the convenience of welding?-Certainly, you may weld a large bar together, and I think

with attention you may make it as strong as any other part.

Have you any doubt, whether a square bar may be equally well welded with a round one; and if you think there is any difference, can you give any opinion as to the amount of the difference?—I do not think there will be any difference.

Have you any reason to believe, that if a square bar or bolt of any certain length would require 100 tons to separate it, two or any greater number of bars added together would not require nearly an increase of four in proportion to the number of bars so united ?There is no question that they would bear equally, provided the force should be equally applied to them at the same time, but if there is the least deviation from that, of course the strain comes all on one.

Are you aware of any difficulty in adding bars together longitudinally by the side of each other, so as that the strain upon each should be nearly equal, and sufficiently so to be reckoned upon with safety?—I think that they may be laid one at the side of the other, so that they would come all to one bearing; and if there was one bore more stress than the other, it would most likely stretch till the bearing came equal upon the whole.

You conceive it practicable to form any reasonable number of bars into one cable, so as to acquire a strength sufficient for any given purpose?-I should have a doubt in welding a piece of iron, when you come to such an immense length as 500 feet, whether there would not be a difficulty in the working of it; a piece of iron, in order to make a sound weld of it, ought to be turned round and hammered; but it is impossible to turn round a piece of iron of which there is 500 feet.

Do you or do you not apprehend, that a die might be

made

made to receive the bars, or some other mechanical means practised, by which the weld might be made sufficiently strong for any practical purpose?—I should still have my doubts with regard to making it so strong as the other part of the bar, which is drawn regularly through the rollers.

Supposing means to be invented, of turning a long bar as perfectly and as frequently as a short bar could be turned, should you then entertain those doubts, and to what degree?—I should still doubt; I do not think it is possible to move such a large piece of iron as that so quickly out of the fire, and to take a force upon it, without the heat being considerably gone; the heat is gone in two seconds.

It depends then, according to your idea, upon the degree of celerity with which the hammer can be applied to the iron, when in a fit state for welding?-Decidedly so.

If this difficulty of applying the hammer with sufficient quickness were surmounted, does any other appear to your mind? If those objections which I have started can be got over, I do not see any other.

You make iron cables?-We do.

What strain are your largest iron cables calculated to bear? What we make for the first-rate men of war, will carry about 200 tons.

Are they chain cables?—Yes.

What is the cubical content, or more properly the section of the weakest part of that chain cable?-Two inches and 1-8th in diameter; the proof that we put upon that is 110 tons.

You mean, then, that having proved it as far as 110 tons, you conclude by calculation on its dimensions, that it is capable of carrying 200 tons?-We do, and beyond VOL. XXXV.-SECOND SERIES. that

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