PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 361 



Russ pavements that are laid square with the street, a cab lost one pound 

 from its tires while its horse lost seven pounds from its shoes. The cab at 

 that time weighed 1,050 lbs., or about 1,350 lbs. when loaded, say a third 

 of the weight of a loaded omnibus. 



Taking as unity the dirt made by the wheels of a cab, we have the fol- 

 lowing as the relative quantities worn from pavements by the different 

 modes of conveyance we have to consider. But we have to add the 

 manure dropped by the horses, which was found by analysis to be a third 

 of the whole dirt. The dirt worn from the pavement by a cab and horse being 

 equal to eight, we must add four, making twelve, — one for cab and eleven 

 for a horse. And in estimating for rail cars we may assume that, one car 

 does the work of three omnibuses, and that its wheels make no sensible 

 amount of dirt. Therefore for 



3 omnibuses equal to 1 car •. 9 



6 horses, the dirt is equal to 66 



Total 75 



1 two-horse rail car 22 



1 steam car 



This comparison shows that the street railway system by horse power, 

 as now practiced, makes less than 29 per cent, as much dirt as the omnibus 

 system; and that steam cars, which are likely to be sanctioned by the 

 legislature, will reduce to nothing the ordinary dirt; and I shall show 

 that there need not be any sensible amount of dirt of other kind from them. 

 So far as this part of the traflSc is concerned, it is satisfactory as to the 

 dirt nuisance; but we have goods traffic and private vehicles to pro- 

 vide for, and it is not pretended that these can be accommodated by rail- 

 ways: we are still required to keep up the dirty system for this part of 

 the traffic, and are to be relieved only from so much dirt as is made by 

 the cars and omnibuses. 



I have long advocated iron flooring on the streets. No dirt could come 

 from this floor; and the dirt thrown upon it could be easily swept clean 

 off". On an iron floor a man could do more than a horse can do on the Russ 

 pavement; but steam power is the cheapest, as well as the best; and I 

 anticipate the use of steam wagons and traction engines for all kinds oi* 

 traffic. And steam carriages and wagons have this advantage over the 

 railway s^'stem, that they can be introduced without disturbance of the 

 existing order, and can gradually displace horses, as horses and their 

 vehicles are worn out. 



On stone pavements, steam carriages will make some dirt, but not of the, 

 most offensive kind: it will be pulverized granite, without manure in it. I 

 consider that a steam omnibus will weigh one-half more than a horse 

 omnibus, and its dirt may be represented by 4i, or 13i for a steam carriage 

 equal in capacity to a rail car. The relative dirt will be: 



B\' horse omnibuses on stone pavements 100 



steam do do 18 



horse rail cars 28f 



steam do 



steam on iron pavements 



