TUBES AVITH A CORRUGATED TOP.

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on my return to Manchester; and the results will throw a little lightupon the subject and enable me to judge better of the anomalies in yourtube experiments. There appears to me, however, to be a great want offundamental information on the subject.

I am, my dear Sir, yours most truly,

William Fairbairn, Esq. Eaton Hodgkinson .

Postscript .—I am much in want of a book, “Navier’s Application deMecanique.” I have thought of sending home for it; but perhaps bythe time it arrived, I should be ready to return. I know there is some-thing to my purpose in “ Navier.” You have the book likewise.

Mr. Hodgkinson did not experiment upon these tubesalthough they were constructed for him, since he found, fromthe experiments which had already been recorded, that therectangular forms Avere decidedly the best; accordingly themodels subsequently made for him were of this form. The in-terval of time Avhich ensued, betAveen the experiments on therectangular and elliptical tubes Avith single cells, and those onthe tube Avith a corrugated top, was chiefly occupied in pre-paring this latter tube for experiment. On the 14th of Octoberit was subjected to the usual tests, as explained in the folloAvingletter addressed to Mr. Stephenson.

My dear Sir, Manchester, Oct. 15, 1845. Fig. 13.

Our experiments of yesterday were the bestand most satisfactory we have yet made; andagreeable to expectation, the form, as per an-nexed sketch, gave not only the greatest strength,but what was of equal importance, there was anear approximation to an equality of the forceson the top and bottom sides.

The figure, you will observe, was in strictaccordance with the views contained in myletter, which followed our previous efforts; thesection being a rectangular figure, as above,with a double corrugated plate, each plate for

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