30 aiECHANICS. 



Although the preceding table gives the strength of wood 

 drawn lengthwise^ yet the comparative results are not 

 greatly different when the force is applied in a transverse 

 or side direction, so as to break in the usual way. 



The following table shows the results of several experi- 

 ments with pieces of wood one foot in length, one inch 

 square, with the weight suspended from one end, breaking 

 them sidewise. 



White oak, seasoned, broke with 240 lbs. 



Chestnut, " " 170 " 



Whitepine, " " 135 " 



Yellow pine, " " 150 " 



Ash, " " 175 " 



Hickory, " " 270 " 



A rod of good iron is about ten times as strong as the 

 best hemp rope of the same size. The best iron wire is 

 nearly twenty times as strong as a hemp cord. Hence the 

 enormous strength of the wire cables, several inches in di- 

 ameter, which are employed for the support of suspension 

 bridges. 



A rope one inch in diameter will bear about 5000 lbs., 

 but in practice should not be subjected to more than half 

 this strain, or about one ton. The strength increases or 

 diminishes according to the size of the cross-section of the 

 rope ; thus a cord half an inch in diameter will support 

 one quarter as much as an inch, and a quarter-inch cord a 

 sixteenth as much. A knowledge of the strength of 

 ropes, as used by farmers in windlasses, pulleys, drawing 

 loads, etc., would sometimes prevent serious accidents. 

 The following table may therefore be useful : 



Diameter of rope or Fovnds borne Breaking 



cord in inches. with safety. weight. 



One-eighth 31 lbs. 78 lbs. 



One-fourth 125 " 814 " 



One-hulf 500 " 1250 " 



One 2000 " 6000 " 



One and a quarter 3000 " 7500 " 



One and a half 4500 " 13,500 " 



