PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 321 



Flonrinj^ Mills, at tlic expense of the owner, Mr. Ilecker, in which steam 

 is used in a steel cylinder which is kept hot by a steam jacket — the gain 

 by the cut-off thus far is 25 per cent; he would not then enter into details, 

 as the members of this association were to be invited to witness the prac- 

 tical operation of this engine. 



Dr. K. S. Newton, after giving an account of some experiments made 

 with double cylinders on Western waters, which were all unsuccessful, di- 

 rected attention to the cause of explosions of boilers, and alluded to the 

 disaster on the United States steamer Chenango. 



Mv. Watson made a diagram on the black-board illustrating the manner 

 in which tlie boilers on the Chenango were braced, as adduced from the 

 evidence before the Coroner's Jury. It was very evident that explosion 

 was caused bj- a defi'^iency in the bracing. A sfi'ain of nearly ten tons was 

 brought upon each iron strap, having only five-eighths of an inch sectional 

 area, to which the braces between the arches of the fire-box and the flat 

 shell of the boiler were connected, and they naturally gave way in conse- 

 quence. There were but 32 of these straps instead of G4; just half the 

 number called for in the specifications, and the disaster which occurred is 

 the result of the omission. By the acceptance of the boilers by the Govern- 

 ment agent, the contractors are relieved from all responsibility in the 

 matter. 



After some further desultory debate upon boiler explosions, on motion of 

 Mr. Bartlett, "The best mode of producing heat" was selected for discus- 

 sion at the next meeting. Adjourned to June 2. 



Americax Institute Polytechxic Associ.\tiox, ) 

 Jime 2d, 1864. j 



Chairman, Prof. S. D. Tillman; Secretary, Mr. B. Garvey. 



Improvement of Broadway. 



The Chairman offered some considerations on the feasibility of improving 

 the grade of Broadway. The steepest grade on this great thoroughfare, 

 after Ipaving Bowling Green, is between Leonard and Canal streets. It 

 was considered unsafe to put down the Russ pavement over this portion of 

 the street, and the smaller trap-rock block known as the Belgian was sub- 

 stituted. These small stones, about six inches square on the surface, give 

 the horse a better foothold, but they do not prevent his slipping and fall- 

 ing. Such blocks are objectionable, because they cannot resist the pound- 

 ing they receive from heavy vehicles; they are thrown out of place; their 

 edges are chipped off, and the surface is as rouuded as that of a cobble- 

 stone. The poorest pavement on Broadway is, without doubt, the Belgian, 

 but it is used because larger blocks cannot be made safe on so steep a 

 grade. 



To the query now presented. Can this evil be obviated ? this reply may 



be made. From Leonard street to Duane there is a descent of several t'net. 



Let this summit on either side of Leonard street be cut dcnvn so that 



there shall be no higher line than Duane street, or let the grade be a gr:idual 



[Am. Inst.] U 



