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MERICA, woefully in the rear of progress in rock surfacing her highways, had built less than 30,000 miles of macadam roads out of a total mileage of 2,150,000 when from the hazy realms of invention came a combined menace and blessing in the shape of the motor car.

This modern chariot of gasoline, with fat, wind stuffed tires was quickly derided by such near sighted folk as are unable to identify a blessing if it comes at all disguised, but highway engineers, while appreciating its civilizing influences, soon discovered that the new machine was an enemy to all hard surfaced highways and that those responsible for them were confronted by the greatest problem they had ever been. called upon to face.

Since the fact was made plain to these men that the onward rush of the automobile was ravelling the rock surfaced roads of Christendom and was doing a damage that ran to scores of millions of dollars annually, various experiments have been made to overcome the effects created and the most interesting ever held were conducted by Logan Waller Page, Director of the Office of Public Roads of the United States Department of Agriculture, on Hillside Avenue, Jamaica Heights, at Long Island on May 20; the distinguished Federal expert being assisted by members of the engineering corps of the United States army; by experts of the agricultural department and by distinguished scientists who went to the scene of the startling experiments as guests of the Federal officials and of the American Automobile Association; that great organization having extended to Director Page, its good offices and influence in securing fast cars, skillful drivers and a suitable

location in which to carry on the desired experiments.

For seven hours there followed a succession of interesting trips over a measured stretch of one tenth of a mile of road; the passages of the motor cars, horse drawn vehicles, saddle horses and motor cycles being noted with scientific exactitude and innumerable pictures being taken in the hope of learning exactly what deleterious effects various types of vehicles and various tires have on highway surfaces.

Among those who deemed these experiments of enough importance to draw them from various states and cities to assist or observe were: Colonel Spencer Cosby, Superintendent of Buildings and Grounds, Washington; Major Jay Johnson Morrow, Corps of Engineers, U. S. Army; David Sheridan Stanley, Major Quartermaster, U. S. Army; Lieutenant Warren T. Hannum, Corps of Engi neers, U. S. Army; Vernon M. Pierce, Chief Engineer, Office of Public Roads, Washington; Dr. Lyman J. Briggs, Physicist, Department of Agriculture, Washington; James C. Wonders, State Highway Commissioner of Ohio; Col. William D. Sohier, State Highway Commissioner, Massachusetts; Francis A. Price, State Highway Commissioner, Delaware; P. St. J. Wilson, State Highway Commissioner, Virginia; Alex. Floyd Armstrong, State Department of Highways, Albany; R. D. Beman, Deputy State Highway Commissioner, Pennsylvania; James Owen, representing the State Commissioner of Roads of New Jersey; James R. Rablin, Chief Engineer of the Metropolitan Park Commission; George Lyman Rogers, Counsel of the Metropolitan Park Commission; Jesse T. Vogdes, Chief Engineer and Superintendent of Fairmount Park, Philadelphia; John J. Laughlen, Chief Engineer Borough of Queens; George C. Diehl, Engineer, Erie County

and Chairman of the Good Roads Committee of the American Automobile Association: Herman F. Cuntz, of the Associated Licensed Automobile Manufacturers; Coker F. Clarkson, of the Engineering Department of the Associated Licensed Automobile Manufacturers; Charles Shaddlen Ferry, Chairman of the A. A. A. Legislative Board; Frederick H. Elliott, Secretary of the A. A. A., and John P. Coghlen, President of the Worcester Automobile Club.

After having made the statement that the soft rubber tires of an automobile are more damaging to a road surfaced with a hard rock than are the iron tires of a horse drawn vehicle it is advisable to become historic and scientific to the extent of a few paragraphs to explain why.

The theory on which those great engineers of former days, Tresaguet of

Limoges, and Macadam of Ayrshire, worked was that the constant passing of iron shod horses drawing iron tired vehicles would improve rock surfaced roads, and though methods of construction vary today in different countries road engineers have always had in view one main object, the withstanding of the wear of iron tired vehicles. For a century and a half the conditions were successfully met and the stone road did all that was expected of it.

The reason is plain when understood. Under the passing of wagons equipped with iron tires the surface rock was constantly being fractured; the tiny dust particles so formed sifting their way into the interstices and being packed firmer and firmer in place by rains and traffic, finally forming a cemented, bonded, impervious, impervious, water - shedding shell. When in its highest state of per

lift the dust binding surface and send it. swirling away, while the soft rubber tires. crush no rock to supply that which they strip from the highways.

One of the first to discover these new conditions and to appreciate the importance of devising a way to conquer dust making propensities of the automobile was Director Page. He was studying conditions when he received word that France had awakened to the tremendous importance of overcoming the conditions, for the roads of that countrybuilt at a cost of approximately $662,000,000 had retrograded in a dozen years fully thirty-three and one-third per cent a loss of about $220,000,000.

claimed, but the tremendous tractive force exerted by the rear, or driving wheels of the car; that power causing the wheels to shear the road surface.

Recently more tests were held in Washington, various types of cars being sent at varying rates of speed over both common macadam and the oil surfaced macadam roads and instantaneous pictures being taken of the front and rear tires as they passed over certain specified points. News of these experiments created a desire on the part of the A. A. A. to co-operate with the government and a delegation sent to Washington persuaded Mr. Page to arrange for the recent Long Island tests and to invite

sults of the mathematical calculations now being made.

Much stress has been laid upon the effect of the car body and its shape in lifting dust from the road surface. Some experiments seem to furnish convincing proof that but little dust is taken from the roads by this means, though the dust. lifted by the wheels is greatly accelerated by the action of the car body and the air currents set up in its rear. This must be considered an important factor, as much of the dust lifted by the wheels would not be carried from the road but for the air currents developed by the peculiar shape of the body of the car.

To gain proofs of the above beliefs and to gather information on which legislation may be wisely based was the purpose of the day, and the reasons

ing on results was considered and all car weights, dimensions of wheels and tires were recorded. There were thirty-seven separate events. The first were to determine the amount of dust raised by motor cars passing a given point at varying rates of speed, both with the clutch in place and with the power thrown off so that the car would coast past a given point; also by motor cycles; by teams and by a saddle horse passing at from ten to twenty-five miles an hour.

It was plainly observable that when the heavy cars passed over the road at speeds in excess of twenty-five miles an hour the tractive force of the rear wheels raised the road surface and caused windrows of dust to form, that damaging effect depreciating to a marked degree as soon as the clutch was

released and the car allowed to proceed on the momentum gained before the power was shut off.

In the many tests cars were sent over the road at rates ranging from ten miles an hour to seventy-eight; that speed burst being made by a car driven by Ralph de Palma, while another driver made seventy-one. These speeds were recorded by a chronograph operated by Dr. Lyman J. Briggs, Physicist of the department of agriculture, who proved with his delicate speed-measuring apparatus that the modern speedometer flatters car owners to an amazing degree; the speed measuring dial on the fastest car recording a speed of eightyeight miles.

The braking tests were interesting. They made it plain that no man has any right to speed a heavy car along any highway at a rate exceeding twenty or twenty-five miles an hour, for at higher rates of speed it is impossible to bring one to a stop even with the strongest emergency brakes in such a distance as to avert accidents in case teams, other cars or pedestrians suddenly appeared in the path of the oncoming machine.

These braking tests were conducted at varying speeds. The best stop made. at forty miles an hour was one hundred and forty feet. At a speed of thirty miles an hour one car was stopped in

seventy-four feet. That showing was exceedingly creditable, however, when it its noted that a splendid horseman was only able to bring his mount to a full stop in one hundred and fifty-two feet after running him at the rate of twentyfive miles an hour, while a motor cycle proceeding at forty miles an hour was checked in one hundred and fifty-seven feet. A two horse team going ten miles an hour was checked at twenty-seven feet.

The results will be collated and with deductions drawn by experts will be furnished to legislative boards in all sections of the land where legislation is being considered. They will be of value in determining what laws should be passed to guard the roads and to ensure a greater degree of safety for pedestrians and drivers.

Dusty roads existed before the motor vehicle was ever thought of, but automobiles have aggravated this condition. They are in no wise to be condemned, however, for while the above facts may by some be regarded as an arraignment of the automobile, in its relation to public roads, it must not be forgotten that the application of mechanical arts which work for the comforts and convenience of civilization must inevitably produce new problems, and those must be solved by patient experiment and by many tests.