THE USE OF IRON. 57 



siderations, and as these last are governing factors in this 

 practical age, a comparison is certainly not complete without 

 considering market values or intrinsic worth of the two metals. 



One of a set of specifications calling for proposals for 

 wrought-iron stand-pipe construction was issued in October, 

 1897, the dimensions of the pipe being 15 ft. by 1 10 ft., 

 the metal to conform to the following requirements: 



" The material of which the stand-pipe shall be built shall 

 be a good, sound, rolled plate, having a tensile strength of not 

 less than forty-eight (48,000) thousand pounds per square 

 inch of section ; elastic limit, twenty-four (24,000) thousand 

 pounds; elongation not less than 15^ in a full section of test- 

 piece 8 in. long, and on examination show no sign of inferior 

 workmanship. Each plate shall be stamped with the name 

 of the manufacturer and its tensile strength." The shop to 

 whom the award was made furnished at the same time an al- 

 ternate proposal for steel plate under the following manufac- 

 turers' guarantee : 



Steel plate -f^ in. to ^in. T. S. 60,000 to 66,000 Ibs. persq. in. 

 " " " T V* T. S. 54,000 " 58,000 " " " " 

 " T 5 F " " f " T. S. 56,000 " 60,000 " " " " 

 " j\ " and upward 58,000 " 64,000 " " " " 



Elastic limit more than ^ T. S. 



Elongation, 8 in. section (at least), 2O# for all plates over f in. 

 thick. 



Reduction of area, at least 5$- 



The market prices of the two metals at the date of these 



proposals were as follows f. o. b. cars at mills : 



Steel plate, $1.05 per loolbs. 



Iron plate $1.40 ." " " 



Iron rivets 50 cts. per 100 more than steel. 



The estimated weights of the stand-pipe material were as 

 follows : 



