362 ROADS. 
value will be proportioned to their solidity and du- 
rability, it is essential that he should understand 
the absolute and relative strength of materials, the 
resistance they offer to friction and shocks, the 
changes which they undergo from exposure to the 
atmosphere, and to the more ordinary chemical 
agents, such as fire, salt water, &c., as well as the 
time and labour required in preparing them for the 
purposes of building. 
Boads. — It has been well remarked, " that the 
expense of constructing a new road, or of main- 
taining an old one in good order, greatly depends 
upon the kind of ground under it, upon the facility 
with which proper stone may be obtained for it, and 
upon the stability of the various cuts which it may 
be found necessary to make in the rocks, is well 
known. It is not, however, so well known, that 
these circumstances depend upon the geological 
structure of a country, and that a knowledge of this 
structure would enable those who possess it to de- 
termine whether one line of a new road would be 
more costly than another; whether, when it be- 
comes a question to patch up an old line of road or 
construct a new one, the one or the other will be 
ultimately found least expensive ; and that some 
kinds of stone should be employed upon roads in 
preference to others, when several kinds can read- 
ily be obtained." An attention to these particu- 
lars, however unimportant they may appear to 
some, would save in this country many thousands 
of dollars annually. Those who have travelled 
much, and seen how our roads are constructed and 
repaired; how, in some places, a soft, perishable 
stone is brought from a distance, when a far better 
material is close at hand ; how slatestone and 
graywacke are often beaten up, and used either for 
the foundations or repairs of common or even Mac- 
adamized roads, which are soon pulverized, forming 
an impalpable dust in dry weather and a miry clay 
