368 PROCEEDINGS OF THE AMERICAN ACADEMY 



century, before which time, indeed, none were used in this country. 

 Younger men than I can well remember when there was not a 

 cast-iron pillar bearing up a single wall or floor in Boston, though 

 they now constitute the principal support of enormous piles scattered 

 through every street. In England the use of cast-iron commenced 

 somewhat earlier than in this country, as the material was there much 

 cheaper, and the art of founding it practised more perfectly. In both 

 countries, however, it was used with much caution. The engineers 

 best acquainted with it knew its uncertain, not to say treacherous 

 character. They proceeded, therefore, with great caution, taking care 

 to make a great allowance for defective workmanship, and the dis- 

 turbing influences of change of temperature, movements in foundation 

 walls by the yielding or freezing of the earth, vibrations from moving 

 loads, and the motion of machines, and other influences. By this 

 cautious mode of proceeding they kept within the limits of safety, 

 though sometimes, no doubt, with a prodigal use of iron. 



It seems that in the year 1795, Mr. Reynolds, a well-known 

 engineer, made two or three experiments upon the powers of bars, 

 one inch square and three feet long, to sustain weights pressing upon 

 them endwise. But these experiments are not related with sufficient 

 detail to have furnished any useful conclusions. 



In the year 1818, Mr. George Rennie published in the Philosophi- 

 cal Transactions an account of his experiments on the power of cast- 

 iron to resist a crushing force. These experiments were confined to 

 small specimens in the form of cubes and prisms. The largest cubes, 

 having sides of one fourth of an inch, being crushed by 12,6G6 pounds, 

 and the largest prisms, of one fourth of an inch base by one inch in 

 height, being crushed by 6,440 pounds. Experiments like these would 

 form a very insecure foundation for any rule to determine the strength 

 of long columns, however, because such columns are not destroyed by 

 being really crushed, but by being crippled by the compressing force, 

 bending sidewise and breaking transversely. 



About two years after the publication of Mr. Rennie's paper, Mr. 

 Tredgold, a man who attained, and that deservedly, a high reputation 

 as a writer upon engineering, endeavored to find from the very scanty 

 materials then existing, by geometrical methods, the absolute strength 

 of cast-iron pillars of all sizes ; and to give rules to be used by prac- 

 tical builders, that should be trustworthy for their guidance. Mr. 



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