Asphaltic and Wood Pavements. 39 
roadways are more easily repaired than any other kind of 
pavement. 
Wood paving, with its numerous joints and comparatively 
soft and elastic surface is satisfactory as regards noise and 
foothold for horses, though in certain conditions of the 
atmosphere it may become quite as slippery as asphalt, and 
it is not adapted for steep gradients. It has the tremendous 
drawback that it is porous and does not dry rapidly unless 
treated very carefully with creosote or other materials which 
are used to close to some extent the pores of the wood and 
prevent its decay. In spite of such precautions, and to 
some extent on account of them, the dust from streets with 
wood pavement is very offensive and irritating to the eyes 
and throat in long-continued dry weather. Breaches made in 
wood paving are difficult to repair in a neat and satisfactory 
manner ; and as it is also a matter of the utmost difficulty 
to secure blocks with uniformity of resistance to wear, it is 
remarkable that wood paving should retain the hold it has on 
the favour of many city engineers. It is supposed to have 
an advantage over asphalt paving when tram rails are 
laid in streets, but in Berlin, and elsewhere, tramways have 
been successfully laid in asphaltic paving, with and without 
lines of stone alongside the rails. In Australia, whence come 
the hard woods most in favour for street paving for heavy 
traffic, wood paving was stated to be practically discarded a 
few years ago. In America brick paving and a special kind 
of asphalt are in general use in preference to the forms of 
paving most commonly used in Europe. 
The modern American asphaltic work is carried out with 
natural bitumen obtained in Trinidad, where a large deposit 
of this valuable material is found in a comparatively small 
area from which, between the years 1893 and 1902, about a 
million tons of bitumen have been obtained, mainly for paving 
works in America, but partly for use as an insulating material. 
Professor Louis, of the Armstrong College, estimates that the 
supply is not inexhaustible, but that there should be about 
fifteen million tons of bitumen remaining in the Pitch Lake, 
which is the principal source of supply, and has an area of 
about 140 acres. In forming asphaltic roadways in America, 
from 12 to 15 per cent, of refined Trinidad bitumen is mixed 
with 70 to 80 per cent, of sand and 5 to 15 per cent, of lime- 
stone dust. These materials are heated and stirred together 
into a stiff mastic paste, which is laid two inches thick on top 
of a first layer of finer stuff of the same nature, applied to the 
concrete foundation to unite the wearing surface thereto and 
prevent “ creeping.” This process requires great judgment and 
experience, but the same may be said of any street pavement 
