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Article TO SIR GEORGE STAUNTON, BART. ← Page 4 of 6 →
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To Sir George Staunton, Bart.
" - The arch having thus gained nearly a solid bearing on the wood and the butments , and the days beginning to be warm , and the nights con ? tinuing . to be cool , I had how to observe the effects of the contraction and expansion of the iron . ¦ ' The 'Academy of Sciences at Paris , in their report on the principles and'construction of this arch , state these effects as a matter of perfect indifference to the archor to the butmentsand the experience
esta-, , blishes the truth of their opinion . It is probable the Academy may have taken , in part , the observation ' s of M . Peronnet , architect to the King of France , and a member of the Academy , as some ground for that-opinion . From the observations of M . Peronnet , all arches , whether of stone or brick , are constantly ascending or descending by the changes of the weather , so as to render the difference perceptible
Try taking a level , arid that all stone and ' brick buildings do the same . In short , that matter is never stationary , with respect to its dimensions , but when the atmosphere is so ; but that as arches like the tops " of houses are open to the air , and at freedom to rise , and all their wei g ht in all changes of heat and cold is the same , their pressure is very little of nothing affected by it . I hung a thermometer to the arch where it has continued several days , and by what I can observe it equals if not exceeds the
thermometer in exactness . : ' In twenty-four hours it ascends and descends between two and three tenths of an inch at the center , diminishing in exact mathematical proportion each way ; and no sooner does an ascent or descent of half a hair ' s breadth appear at the center , but it may be proportionally discovered through the whole span of 90 feet . I have affixed an index which multiplies ten times , audit can as easily be multiplied
an hundred times : could I make a line of fire on each side the arch , so as to heat it in the same equal manner through all its parts , as the natural air does , I would try it up to blood heat . " Twill not attempt a description , of the construction : first , because you have already seen the model ; and secondly , that I have often observed that a thing may be so very simple as to baffle description .
Oh this head I shall only say , that I took the idea of constructing it from a spider ' s web , of which it resembles a section , and I naturally supposed , that when nature enabled that insect to make a web , she taught it the best method of putting it together . < " Another idea I have taken from nature is , that of increasing the strength of matter by causing it to act over a larger space than it
would occupy in a solid state , as is evidenced in the bones of animals , quills of birds , reeds , canes , & c- which , were they solid with the same quantity of matter , would have the same weight with a much less degree of strength . I have already mentioned that the quantity of iron in this rib is three tons ; that an arch of sufficient width for a bridge is to be composed of as many ribs' as that width requires ; and that the number ofarches , if the breadth of a river requites more than one , may be multiplied at discretion , •' -. ' ,
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
To Sir George Staunton, Bart.
" - The arch having thus gained nearly a solid bearing on the wood and the butments , and the days beginning to be warm , and the nights con ? tinuing . to be cool , I had how to observe the effects of the contraction and expansion of the iron . ¦ ' The 'Academy of Sciences at Paris , in their report on the principles and'construction of this arch , state these effects as a matter of perfect indifference to the archor to the butmentsand the experience
esta-, , blishes the truth of their opinion . It is probable the Academy may have taken , in part , the observation ' s of M . Peronnet , architect to the King of France , and a member of the Academy , as some ground for that-opinion . From the observations of M . Peronnet , all arches , whether of stone or brick , are constantly ascending or descending by the changes of the weather , so as to render the difference perceptible
Try taking a level , arid that all stone and ' brick buildings do the same . In short , that matter is never stationary , with respect to its dimensions , but when the atmosphere is so ; but that as arches like the tops " of houses are open to the air , and at freedom to rise , and all their wei g ht in all changes of heat and cold is the same , their pressure is very little of nothing affected by it . I hung a thermometer to the arch where it has continued several days , and by what I can observe it equals if not exceeds the
thermometer in exactness . : ' In twenty-four hours it ascends and descends between two and three tenths of an inch at the center , diminishing in exact mathematical proportion each way ; and no sooner does an ascent or descent of half a hair ' s breadth appear at the center , but it may be proportionally discovered through the whole span of 90 feet . I have affixed an index which multiplies ten times , audit can as easily be multiplied
an hundred times : could I make a line of fire on each side the arch , so as to heat it in the same equal manner through all its parts , as the natural air does , I would try it up to blood heat . " Twill not attempt a description , of the construction : first , because you have already seen the model ; and secondly , that I have often observed that a thing may be so very simple as to baffle description .
Oh this head I shall only say , that I took the idea of constructing it from a spider ' s web , of which it resembles a section , and I naturally supposed , that when nature enabled that insect to make a web , she taught it the best method of putting it together . < " Another idea I have taken from nature is , that of increasing the strength of matter by causing it to act over a larger space than it
would occupy in a solid state , as is evidenced in the bones of animals , quills of birds , reeds , canes , & c- which , were they solid with the same quantity of matter , would have the same weight with a much less degree of strength . I have already mentioned that the quantity of iron in this rib is three tons ; that an arch of sufficient width for a bridge is to be composed of as many ribs' as that width requires ; and that the number ofarches , if the breadth of a river requites more than one , may be multiplied at discretion , •' -. ' ,