demonstrate the great advantage of wide tires over narrow tires. Several of these experiments taken from Circular No. 31, U. S. Department of Road Inquiry, are here given :

"Onondaga County, New York, furnishes an interesting illustration of the value of wide tires as road-rollers. The Solvay Process Company, of Geddis, in that county, was accustomed to hauling heavy loads of stone, for four and a half miles from the quarry. To test the wide-tire theory, they built several wagons having 4inch tires on the front wheels and 6-inch tires on the rear wheels, and with the rear axles longer than the others, so that the track of the rear wheels would just lap outside of those made by the others. The result of the use of these wagons was to produce a hard, smooth, compact surface; and the road, having been filled, so as to raise the middle, or "crown" it, is thoroughly drained at the surface, and always fit for use with the heaviest loads. Loads of 8 tons are frequently hauled over them, and instead of tending to cut up the road, serve to roll it harder and harder. The superintendent reports, too, that the improved condition of the road has reduced the cost of hauling the stone from 80 cents per ton to 60 cents, or 25 per cent.

"It has also been proven by experiments upon a number of occasions, that the use of wide tires considerably reduces the amount of power required to move loaded wagons. One of these tests was made by the officers of the U. S. Department of Agriculture at the Atlanta Exposition in 1895. Two wagons, both weighing alike with their loads, were drawn over a wet piece of clay road, one wagon having 2-inch tires, the other, with 4-inch tires and with the rear wheels farther apart, than the front wheels, so as not to run in the same track. It was found by the use of the tractometer, an instrument made to register the power exerted, that twice as much pull was required to haul the 2-inch tired wagon as was required for the other. That part of the road traversed by the narrow-tired wagon was cut and rutted to a depth of several inches, while the tires of the other wagon had rolled the road into a smooth and hard surface.

"The Missouri Agricultural Experiment Station made a series of tests, extending from January, 1896, to September, 1897, in order to thoroughly and scientifically ascertain the value of wide tires as compared with narrow ones. They were made with two wagons, one with 6-inch tires, the other with standard 1 1⁄2-inch tires, both wagons of the same weight, and each loaded with 2,000 pounds. It was found that the same power needed to draw the narrow-tired wagon, with its 2,000-pound load, on a gravel road, would have pulled a load of 2,482 pounds on the wide-tired wagon. The same power, required to draw the 2,000-pound load, on narrow tires, over dirt and gravel roads, when these were dry and hard, was found sufficient to draw a 2,530-pound load on the wide-tired wagon under the same conditions; and it was shown, that, when these roads were deep with mud, but partly dried at the surface by a few hours' sun, the same power, required to draw the 2,000pound load over them, on the narrow tires, would pull a load of 3,200 pounds on the wide tires. Director Waters, of the Station, states, that the conditions, under which the narrow tires offer an advantage over the wide ones, are 'unusual, and of short duration," and that, 'through a majority of days in the year, and at times, when the dirt roads are most used, and when their use is most imperative, the broad-tired wagon will pull materially lighter than the narrow-tired wagons.' He states, that 'a large number of tests on meadows, pastures, stubble land, corn ground, and plowed ground, in every condition, from dry, hard and firm to very wet and soft, show, without a single exception, a large difference in draft in favor of the broad tires. This difference ranged from 17 to 120 per cent.' As a result of all experiments conducted, he says: 'It appears, that six inches is the best width of tire, for a combination farm and road wagon, and that both axles should be the same length, so that the front and hind wheels will run in the same track.'

"Experiments made at the Agricultural Experiment Station in Utah have demonstrated, that a 11⁄2-inch tired wagon drew about 40 per cent. heavier, than one with 3-inch tires, and weighing,

with its load, the same as the other.

At the Ohio State Univer

sity, it was shown, that a wagon with 3-inch tires and loaded with 4,480 pounds, could easily be hauled by two horses over an ordinary dirt road in good condition and with a hard surface; while, with a narrow tire, half as much was a full load for a double team." In view of these various experiments, all of which demonstrate conclusively the special merits of the wide tire, there should no longer be any doubt, as to which kind of tire to adopt for common earth-roads.

CHAPTER VII

THE TOPOGRAPHY OF GEORGIA IN ITS RELATION TO THE HIGHWAYS

The cost of building and maintaining highways depends, in a great measure, upon the topography of the country, through which they pass. If the country is level, little or no expense is incurred in grading; while, on the other hand, if the country is mountainous, the chief cost of road-construction is chargeable to this account. High mountains and precipitous ridges often become such obstacles in the way of road-building, that no intercourse or traffic is carried on, between the inhabitants of adjacent valleys, although they may lie only a few miles apart. Frequently, swamps and morasses also are, in like manner, difficult barriers to the way of free communication between localities having a common interest.

In discussing the topographic features of Georgia with reference to highway-construction, it is thought advisable to divide the State into three divisions, namely, the Paleozoic area, the Crystalline area and the Tertiary area. The last embraces both the Tertiary and the Cretaceous deposits of the State. Each of these divisions is named from the geological formation of its respective area, which has given rise to certain well-marked topographic features. The smallest of these divisions is the Paleozoic, lying in the north-western part of the State. It comprises an area of about 3,500 square miles, and includes the greater part of ten counties, all of which are well adapted to agricultural purposes. The rocks of the Paleozoic area consist of limestone, shale and sandstone, originally horizontal, but now compressed into gentle folds having a northeast-and-southwest trend. In places, these folds have been so closely pressed, that the strata have been broken and re

lieved by huge faults, some of which show a total displacement of several hundred feet. This characteristic structural geology of the region explains, in a great measure, the striking topographical features of the area. Its present configuration is due almost solely to surface erosion; but this, in turn, has been conditioned largely by the original folding and faulting of the strata, together with the relative position of the hard and soft rocks.

Dr. C. W. Hayes, of the U. S. Geological Survey, in describing this area, divides it topographically into three divisions: (1) plateaus; (2) sharp edges; (3) undulating or level valleys.

The plateaus are confined to the western part of the area, and include Lookout and Pigeon mountains and a portion of Sand mountain. These plateaus, which have nearly a level surface, are elevated from 2,000 to 2,400 feet above the sea, and terminate in precipitous escarpments rising a thousand feet or more above the adjacent valleys. Owing to the steepness of these escarpments, it is a very difficult matter to construct a road with easy grades, from the valleys to the plateaus; but, when the elevated areas are once reached, the evenness of the surface reduces the cost of construction to a minimum. As the plateaus are nowhere intersected by streams, they form barriers, affecting, more or less, free intercommunication between the adjacent valleys.

The second type of surface, which is confined to the eastern part of the area, consists of a number of sharp parallel ridges, having a northeast-and-southwest trend. The ridges are due to the slow weathering of the upturned edges of hard sandstone, which, in the plateau, lies almost horizontal. The smaller of the ridges are frequently intersected by streams, along which cross-country roads, of easy grade, can be constructed. The main thoroughfares are located in the narrow valleys, where no serious obstruction is presented to road-construction.

The undulating-valley type of surface lies between the plateau on the west, and the sharp ridges on the east. It consists of low, wide, comparatively level valleys, drained by deep, sluggish