Identifier: britishmarsconta00robs (find matches)
Title: The British Mars : containing several schemes and inventions, to be practiced by land or sea against the enemies of Great-Britain ; shewing more plainly, the great advantage Britain has over other nations, by being masters at sea ; to which is added, an appendix, containing a scheme for manning the British navy, with less grievance to the subject; and a scheme to employ seamen ; of a copper mine near Hudson's Bay and of discovering the North-West passage, or determine there is no such passage ; with cautions and directions
Year: 1763 (1760s)
Authors: Robson, Joseph
Subjects: Great Britain. Royal Navy Military art and science Naval art and science Fortification
Publisher: London : Printed for the author, and sold by W. Flexney
Contributing Library: University of Pittsburgh Library System
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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entured alone; them, if I had not knownCarriages, &:c. had gone over before me ; and 1believe there are very few Inftances of Arches fail-ing, but there was fome other Defed than the ArchStones being too lliort ^ and with Refped to M.Belidors and M. Gatitiers Rules for determiningthe Length of Arch-Stones, I cannot help think-ing that better Rules may be found, for, M.fflidcrs■Rules for the Length of Arch Stones, is one twentyfourth of the Width of the Arch, but by this Rule,the Arch Stones in fmall Arches, i. e. from tenFeet wide to thirty, would be too fhort to bear hea-vy Carriages -, for the Arch Stones in aa Arch ofwte Feet wide, would only be five Inches j andntenty Feet wide ten Inches; and in an Arch ofthirty Feet v/ide fifteen Inches, &c But from fortyFeet width to eighty five, M.Behdors Rule will doindifferently v/ell ; and from eighty five upwards,one Twenty fourth Part of the Width of the ArcHmakes the Arch Stones too long. See the followingTable. IN Ck FOLI ORHE
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ty)cwt(nL >^C^,5^, ( i69 ) A Table fhewing the Length of Arch Stonesfor Circular Arches to bear heavy Carriages,from lo Feet width to 120. Width of the Part of the Width Length of the Arch Stones Arch in Feet. of the Arch. in Feet and Inches. F. I.10 _»^ or I o 15 A or I 3 20 : --J. or I 5 25 y\ — or i I o 30 . ^\ — ,. or I 9 35 iV or I JI 40 j- or 2 r 45 ^ or 2 3 -o _i_ or 2 5 55 ■ ^r —■ or 2 7 60 -- — or 2 9 65 ^a —— or ■. 2 11 70 4t — or , 3 I ■ 75 ■ 2T — or —^ 3 3 80 — ^j or 3 S 85 _«_ or . 3 6 go ^V or 3 7 95 ^\ or 3 8 100 —— ^V or 3 9 105 : 3 10 jio 3 n ,15 _ 4 o 120 — r— — > 4 % Thefe Arch Stones are of a fuf^icient Length,efpecially where there is good Mortar and good flat^ough Stones to form a Counter Arch, to keep theShaking of heavy Carriages from the Arch below,and as a good Thick nefs of Mortar and roughStones, are, or ought to be, generally laid upon ( I70 ) the Crown of every Arch. It may be ordered Cothat the rough Mafonr

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