ROAD-BUILDING.

BY JAMES OWEN, C.E.

Before the Am. Soc. C. E., September 21st, 1898.

The question of road construction in latter years has assumed å somewhat different aspect from that which it bore some five or six years ago, when the subiect was rather thoroughly discussed by the members of this society.

Attention should be called to what may be termed the competition in the road question as evidenced by the lowering of the prices for ordinary street pavements. The speaker remembers the time when the cost of building a telford pavement was about $2 per yard. To-day asphalt pavements are being built at a cost of about $1.38 per yard, and the engineer, in selecting a pavement, if he has any discretion in selecting, might suggest to his clients that it might be better in many places to choose a permanent street pavement, at the lower price which it now costs, than an ordinary macadam road. This idea is advanced because it seems to solve a good many problems. The construction of macadam or telford roads extends through different territories and different kinds of population and can be divided into what may be called mural, suburban and rural. Now, each of these kinds of road requires, to a certain extent, a special treatment, so far as construction for the travel and the available funds with which to construct them are concerned, and it seems to the speaker that it would probably be better to confine the discussion to rural roads, because in the future more permanent and less destructible pavements will be substituted in a great many cases where macadam would now be built.

There are two points to which attention should now be calledfirst, the material, and second, the hauling and laying of the material. Some years ago the speaker read a paper before this society and stated that he did not believe in thin pavements or in anything but a telford

pavement, as far as macadam was concerned, in ordinary circumstances. His mind has not very materially changed in this respect and he still adheres to the principle, both in theory and practice.

Mr. Leutze states that he put down an eight-inch macadam road. The speaker hardly thinks this is a wise practice, and believes that a road would be cheaper, very serviceable and would give better results if five inches of telford and three inches of macadam were used instead of eight inches of macadam only. In the first place, in most parts of the country there is available local stone, which is not perishable, which can be used for a foundation, leaving only the final finish of three inches to be provided from other sources. In the speaker's opinion, it is cheaper, in the majority of cases, to build an eight-inch or a ten-inch telford than an eight-inch macadam, and the final results are much better.

The next problem is the question of the selection of stone. It is conceded on all hands that trap-rock is the sine qua non for macadam and telford pavements. There are different kinds of trap-rock, and they work differently in treatment, but it probably will be agreed by all that a trap-rock pavement, if it can be built as cheaply, or even. at a slightly greater cost than other stone, is the best. Certain country roads built with granite of rather a soft quality have been examined by the speaker, which, for the use to which they are put, are quite successful. A well-selected granite in one or two respects is preferable to trap; it is more friable, and, though it wears out a little faster, it does not break up in dry weather, and where it can be had with a short haul there is no specific objection to it. Of course, granite containing too much mica will not be successful.

In a limestone country, if properly handled, properly laid and judiciously finished, successful results can be had with a good limestone road. Its defects are known. It grinds out easier than either trap or granite. It is dusty. It is also known that a limestone road is much preferable to any other construction except either trap or granite. Then there is the local use of the shales and gravels without treatment. Construction of a permanent gravel road on an aboriginal granite foundation can hardly be classified as an engineering improvement in the way of roads. Yet the proper use of gravel, carefully handled, thoroughly rolled and well selected, can make a very satisfactory road for Mr. North's suggestion of nine months in the year, but not for more than nine months. There are also the shales, which