t
CORRESPONDENCE.
9
tensive investigation. These researches require the utmost care; andnew developments, as well as correct results, are only obtained by re-peated trials of an experimental and inductive character. It shall be myspecial province to ascertain the facts, and determine the law whichgoverns the strength and form of this important structure.
Previous to leaving town, I gave orders for an increased number oftubular models to be made of different forms and dimensions. Towardsthe end of the ensuing week they will be completed, and I purpose againcommencing the experiments on Wednesday morning, the 30th inst.,when I hope you will be enabled, along with your father, to attend.
I am, my dear Sir, always sincerely yours,Robert Stephenson, Esq. William Fairbairn.
My dear Sir, July 21st, 1845.
**********
I am glad to hear that you are proceeding with other forms of tubes;I hope some of them, of &n elliptical form, and with thick plates at thetop and bottom, will be tried, for in this way the disposal of the materialwill approach nearly to that of a common 1” girder, which is doubtlessthe thing to be aimed at.
Yours faithfully,
W. Fairbairn, Esq., Robert Stephenson.
At this time, July 19th—21st, a considerable number of ex-periments had been made: nearly the whole of the cylindricaltubes had been tested*, and preparations were then in pro-gress for the rectangular and elliptical forms. The difficultiesexperienced in retaining the cylindrical tubes in shape, whensubmitted to severe strains, naturally suggested the rectangularform; many new models of this kind were prepared and ex-perimented upon, before the end of July f; and others, withdifferent thicknesses of the top and bottom plates or flanches,before the 6th of August \. This is clearly indicated by the date
* See dates of the Experiments on the Cylindrical Tubes in the Appendix.
1' Vide Appendix, Experiments on the Rectangular Tubes.