1888. ] NEW YORK ACADEMY OF SCIENCES. 43 
the excellences of the twosystems. It is, however, unfortunate 
that the two kinds of pavement are mixed as they are, since the 
stone blocks keep the shoes of horses smooth, and then, passing 
on to asphalt, they are liable to slip. 
All city streets in Belgium are paved with stone cubes. The 
material used is generally the ‘‘ Psammite of Condroz,” which 
is tough and durable and yet always has a grain that prevents 
the surface from becoming very smooth. As compared with as- 
phalt, the Belgium pavement is always rough and noisy. 
In London, the question of pavements has been solved by 
long-continued experiments with all kinds of material ever used 
for this purpose, and it is not too much to say that the best ex- 
amples of all the varieties of pavement in use are found there. 
Four kinds of pavements have been adopted, viz.: (1) Granite 
blocks, which are never more than three inches wide and six or 
seven inches long. ‘They are all carefully dressed, nicely fitted 
together and bedded in concrete, so that they furnish a rela- 
tively smooth and durable surface. (2) Wood pavement, which 
is our Nicholson improved. ‘The blocks are pieces sawed from 
fir planks, three inches thick by eight inches wide. These are 
in some cases creasotized, sometimes not; they are closely fitted 
together, being separated only by strips of felt, are bedded in 
concrete and carefully maintained, a defective block being re- 
moyed at once. (3) Zhe Macadam, used on the broad roadway 
along the Thames embankment; it is smooth enough, affords 
good foothold to horses, and is relatively cheap, but it isnothing 
like so clean as the stone or wooden pavements. (4) Asphalt 
pavement. Of this two varieties are in use, in one of which the 
asphalt is mingled with clay or sand, in the other with gravel. 
Most of the asphalt pavement seems to be made from the Seyssel 
or the Sicily asphaltic rock, muchas it occurs in nature. This 
pavement is acknowledged to be the best in London. When the 
roadbed is carefully prepared and the asphalt is skilfully ap- 
plied, streets thus covered are smooth, clean, silent, pleasant to 
ride over, easy for horses, and salubrious. The asphalt pave- 
ment is also durable; it has been stated that horses are more 
liable to slip upon it and that where it is used accidents are 
more frequent, but careful and long-continued observations 
prove the contrary. It will thus be seen that this is nearly a 
perfect pavement, and it isnot surprising thatit is rapidly grow- 
ing in favor. 
The experience of the Old World has clearly shown the people 
of New York how theycan improve the pavements of the city by 
substituting the best for the worst at no enormous cost, and be 
great gainers in many different ways. They have a choice of 
several kinds of material as good as any attainable anywhere. 
