116 



WELLS'S NATURAL PHILOSOPHY. 



In what posi- 

 tion is a rec- 

 t;ingular beam 

 the strongest ? 



That a large body may have the proportionate strength of a smaller, it must 

 contain a greater proportionate amount of material ; and beyond a certain 

 limit, no proportions whatever will keep it together, but it will fall to pieces 

 by its own weight. This fact limits the size, and modifies the shape of most 

 productions of nature and art — of trees, of animals, of architectural or mechan- 

 ical structures. 



262. The strength of a rectangular beam, or 

 a beam in the form of a parallelogram, when 

 its narrow side is horizontal, is greater than 

 when its broad side is horizontal, in the same proportion 

 that the width of its broad side is greater than the width 

 of its narrow side. 



Hence, in all parts of structures where beams are subjected to transverse 

 strain, as in the rafters of roofs, floors, etc., they are always placed with their 

 naiTow sides horizontal, and their broad sides vertical. 



section of which measures a square inch ; in the second column is given the amount of 

 breaking weights, which arc the measure of their strcngtli in resisting a direct pull. 



Name. lbs. i 



1st. Metals ; — 

 Steel, tempered from 114794 to 1.53471. Tin, cast from 



Iron, bar. 



— plate, rolled.. 



— wire 



— • Swedish mal- 

 leable 



— English do. . 



— cast 



Silver, cast 



Copper, do 



— hammered. 

 Brass, cast 



— wire 



— plate 



Gold 



Tin 



531S2 — 84G11 



530-:0 



5ST3C —112905 



72064 

 55S7-3 



IG'243 — 194G4 

 40997 



20.'320 — 373S0 

 37770 — 899G3 

 17947 — 1947-2 

 47114— 5S931 

 6-2-240 



204;)0 — 65237 

 3228 — 6GGG 



Metals ; — 

 Tin, cast. . . . 



Zinc 



Lead, wire. . 



2d. Woods ;— 



Teak 



Sycamore. . . 



Beech 



Elm 



Larch 



Oak 



Alder 



Box 



Ash 



Pine 



Fir 



4736 



'.-820 

 2&43 to 



12915— 1M05 



9630 

 12225 



9720 — 15040 

 10240 



103G7 — 25851 

 114.53 — 21730 

 14210— 2404.S 

 13480- 23455 

 10038 — 149G5 



6991 — 12870 



The following table shows the average weights sustained by wires of different metals, 

 each having a diameter of about one twelfth of an inch ; 



Lead 27 pounds. 



Tin .34 



Zinc 109 " 



Gold 150 " 



Silver 187 pounds. 



Platinum 274 " 



Copper 303 " 



Iron 549 " 



Cords of different materials, but of the same diameter, sustained the following weights : 



Common flax 1175 pounds. I New Zealand flax 2380 pounds. 



Hemp 1633 " | SUk 3400 



The following table shows the weights necessary to crush columns or pillars composed 

 of different metals; the numbers expressed in the second column being the total crush- 

 ing weight in lbs. per square inch : 



Nnme. lbs. lbs. 



2d. Woods:- 



Oak. from 38G0 to 514T 



Pine " 1928 



Elm " 1284 



3d. Stones :— 



Granite " ^70 



Sandstone " 2556 



Brick, weU baked " 1092 



Nun 



lbs. 



lbs. 



1st, Metals: 



Cast iron from 11,5813 to 177776 



Bra^s, fine " 1G4SG4 



Copper, molten " 11 7088 



— hammered. " 10S040 



Tin, molten " 1,^456 



Lead, molten " 7728 



