The New York Rapid-transit Subway

Proceedings.] DISCUSSION ON NEW YORK SUBWAY, 105 occurred to him why they were put so close together, instead of Mr.Read. having longitudinal girders with the stanchions farther apart, and this the Author now explained in his Paper by saying that variations in temperature would have caused difficulties in making closures if longitudinal girders had been adopted. Some years ago Mr. Read was engaged on a railway-contract in which a very large area had to be covered with longitudinal girders, cross girders, and floor-plates. The bays of the cross girders into the longitudinal girders were all made, fitted at the works, and riveted up on the site, but the junction- bays between the longitudinal girders were left open, and were to be closed when the others had been riveted up. He had templates made of all the junction-bays, each bay being about 30 feet by 5 feet, and sent them to the works, where the plates were made and drilled to the templates. The templates were taken in September, when it was fine and warm, and the plates came on to the work about Christmas, in cold weather, and when they came to be put into the junction-bays they were all too short. They were all rejected by the inspector, and Mr. Read was ordered to send them back and obtain new ones. He delayed the matter for some months, until the principal of the works and the chief engineer came on the scene, and then insisted on having the plates tried again. It was a warm day in March; the plates fitted exactly, and the chief engineer turned his wrath upon the inspector who had kept them out all the time. Perhaps the Author had had some such experience as that in his mind when he considered the question of longitudinal girders. As to the Author’s experiments to deter- mine the relative strength of girders carrying loads when embedded in concrete and when free, Mr. Read had been accustomed, in design- ing floors in which concrete was used with steel joists, to reckon that the joists were 25 per cent, stronger when thoroughly embedded in con- crete than when free, and that seemed to have been borne out by the Author’s experiments. Another interesting matter was tire benefici.il effect of rust on iron bars in concrete. Professor Bach of Stuttgart had also found by experiment that the adhesion of dirty bars was greater than that of cleaned bars in about the same ratio as given by the Author, although the actual figures were not so high. Professor Talbot had made some researches in America with reinforced- concrete beams and columns, and had found that the bond meaning the adhesion, no doubt—was about 376 lbs. per square incli for the rough rods, against 147 lbs. per square inch for the clean rolled rods. That was about the same ratio as was given by the Author, who was of opinion that the union of the metal with the cement was so complete that the former was not capable of