10 KANSAS CITY REVIEW OF SCIENCE. 
in clayey and retentive soils, while it is very considerably retarded and the wood 
remains habitually drier and emits less effluvia where the subsoil is sandy and 
porous. 
The most characteristic features and properties of asphalt pavements have 
been briefly summarized and it is not deemed necessary to repeat or enlarge upon 
them here. Professor Fonssagrives remarks that, ‘‘The absence of dust, the 
abatement of noise, the omission of joints—-permitting a complete impermeabi ity 
and thus preventing the putrid infection of the subsoil—are among the precious 
benefits realized by asphalt streets.” 
Upon hygienic grounds, therefore, asphalt conspicuously stands first, stone 
second, and wood third in order of merit. . 
The correct inference from the foregoing discussion is that no one pavement 
combines all the qualities most desirable in a street surface. It cannot be suffi- 
ciently rough, or sufficiently soft, to give the animals a secure foothold, and at the 
same time possess that smoothness and hardness which is so essential to easy 
draught, The advantages of open joints and entire freedom from street filth can- 
not exist together, under any reasonably cheap method of cleansing the surface. 
A pavement of impermeable bl icks, if laid upon a solid foundation, may be 
constructed and maintained in a water tight condition, by thoroughly caulking the 
joints with suitable material, leaving the surface sufficiently rough and open to 
obviate the objection to a continuous monolithic covering, but roughness, com- 
bined with the requisite hardness, is incompatible with the freedom from noise 
attainable with some kinds of acceptable street surface. 
In order, therefore, to obtain the best pavement for any given locality a judi- 
cious balancing of characteristic merits is generally necessary. The best pave- 
ment so far as we now know, for all the busiest streets of a populous city, where 
the traffic is dense, heavy and crowded, is one of rectangular stone blocks set on 
a foundation as good as concrete, or as rubble stone filled in with concrete ; and 
the next best is one of Belgian blocks set in the same manner. 
The best pavement for streets of ample width, upon which the daily traffic is 
not crowded, or for streets largely devoted to light traffic or pleasure driving, or 
lined on either side with residences, is continuous asphalt for all grades not steeper 
than t in 48 or 50. 
If the blocks of compressed asphalt fulfill their present promise, they may be 
able to replace those of stone upon streets where the latter are now preferable to 
a sheet of asphalt on account of the steepness of the grade. 
It has been urged, as an objection to a concrete foundation, that it is diffi- 
cult to take up in order to reach the gas and water pipes. This is true only in 
the sense that good work is not easily taken to pieces. But such a foundation 
when torn up or deranged from any cause, can readily be restored to its former 
condition, and the pavement relaid upon it with all its original smoothness, firm- 
ness, and stability, conditions which do not obtain with any kind of pavement 
laid upon a bed of sand or gravel. — Roads, Streets and Pavements. 
