326 THE POPULAR SCIENCE MONTHLY 



SCIENCE IN THE SEEVICE OF HIGHWAY CONSTEUCTION 



By CLIFFORD RICHARDSON, M.Am.Soc.C.E. 



NEW YORK CITY 



IN a popular sense, a road is a means of communication by vehicle 

 between different localities. To the citizen who ordinarily uses it, 

 aside from considerations of its aspect and surroundings, the condition 

 of the surface and the ease of traction over it have been the main con- 

 siderations. He has given little thought to the manner in which it has 

 been constructed and has been, usually, quite indifferent to or ignorant 

 of its cost originally or of that for its maintenance. As the use of the 

 automobile has become so general there has recently been a very decided 

 change in this respect. The movement for good roads has arisen and 

 a general interest in the subject has developed. In what follows an 

 attempt will be made, for the benefit of the general reader, to outline 

 the development of the modern methods of highway construction, and 

 to show how science has aided therein. 



The art of highway engineering, that is to say, of the construction 

 of roads, was considered to have been developed to a high degree of 

 perfection at the end of the last century, as evidenced by the magnifi- 

 cent system of broken-stone roads which were in existence at that time 

 in France, more especially, and in England and other foreign countries, 

 while in the United States successful systems of broken-stone roads had 

 been begun in New Jersey, Massachusetts, Connecticut and a few other 

 eastern states. Eoads of this type, when constructed by engineers of 

 experience, with suitable stone, of a proper thickness and with a suffi- 

 cient foundation, properly drained, and when continuously maintained, 

 were found to be adequate to support the severest kind of travel to 

 which they were subjected at that time, at a cost which was not an 

 excessive burden on the state or the taxpayer. The traffic consisted 

 almost entirely of horse-drawn vehicles and the road surface was resist- 

 ant to a degree which would carry this traffic without rapid deteriora- 

 tion. Eoads of this character were known as water-bound macadam, a 

 name derived from their resemblance to the broken stone roads con- 

 structed in England by the celebrated highway engineer John Loudon 

 Macadam in the early part of the last century. Briefly, water-bound 

 broken-stone roads, of the highest type known in the United States, and 

 the only form built until recently to carry heavy travel, are constructed 

 as follows : 



