PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 509 



blocking' np of Broadway by persons having- no business in it, was first 

 •somewhat alleviated by the establishment of the street railway running in 

 a nearly parallel direction; the success of this railway was such as to 

 warrant the establishment of the several lines having their termini near 

 the city hall. 



There arc now three lines of cars on streets adjacent to and on either 

 side of Broadway, which are constantly bearing- away crowds who would, 

 if compelled to walk, naturally keep on this central avenue. 



Another plan for the relief of Broadway, is to make the pavements of the 

 adjacent parallel streets so excellent as to entice into them the travel of carts 

 and loaded vehicles. Should this measure be adopted there would doubt- 

 less still be too great a pressure in the main thoroughfare; yet, with this 

 great evil to be averted, there are those who believe a railroad should be 

 constructed in Broadway. The effect of such a measure would be to vastly 

 increase the travel in that street. What the result will be is not difficult 

 to conjecture. 



The remaining question with regard to the roadway is one to which I 

 have devoted much study. Tiie problem is to construct a roadway which 

 shall be unaffected by frosts, perfectly smooth to all ordinary wheels, and 

 at the same time rough enough to aiTord a foothold for the horse. I have 

 constructed cast iron blocks, which are held together by tongues, so that 

 they cannot move longitudinally, laterally, or vertically, after they have 

 been fitted together. Their surfaces are so indented tliat both the provis- 

 ions of smoothness to the wheel and roughness to the horse shoe, are 

 completely fulfilled. The only objectit)n to this road at the present time is 

 the increased cost of iron; but even now the road can be laid at a less cost 

 than the Russ pavement. On this road a horse can draw more than upon 

 a railroad, because the great friction of the flange, which is vastly increased 

 on curves, is entirely obviated. The number of concussions daily received 

 by an onmibus upon the best Belgian pavement is about half a million. They 

 also affect the horse and passengers. Both carriages and horses would last 

 much longer if these evils were obviated. But the crowning benefit is the 

 absence of noise. 



Dr. D. D. Parmelee. — About ten 3'ears ago, in connection with a friend, I 

 spent considerable time in devising various plans for a railroad in Broad- 

 way, and after considering the subject of using steam, as a motive power* 

 we came to the conclusion that the use of steam, at that time, would not 

 pay, so we directed our attention to compressed air; our plans appeared to 

 be perfect; the cars were to be supplied with air at eacl» end, by a large 

 stationary engine; the pressure of the compressed air was to be regulated 

 by a valve, and we felt confident Ave could run a car from 42d street to 

 Canal with one supply of air. The air was to be compressed very much; 

 and, as our boilers were to be made of steel, and as it is well known that 

 cold steel will stand a greater pressure than when hot, we could, therefore, 

 use a higher pressure of the air than if we used steam. 



The Chairman. — The great difficulty in the way of using compressed air 

 is, that the pressure is varying with every stroke of the engine, so that if 

 the pressure should be only five pounds short, the engine would stop. 



Mr. Rowell. — In 1845 a plan on this principle was tried in Ireland, on 



