--------------------------------+--------+-----------+------------ | Force | | Greatest | in lbs.| Limiting |inclination Description of the Road. |required| angle |which should | to move| of | be given | a ton. |resistance.|to the road. --------------------------------+--------+-----------+------------ | | ° ′ | Well laid pavement | 33 | 0 50 | 1 in 68 | | | Broken stone surface on a bottom| 46 | 1 11 | 1 „ 49 of rough pavement or concrete | | | | | | Broken stone surface laid on an | 65 | 1 40 | 1 „ 34 old flint road | | | | | | Gravel road | 147 | 3 45 | 1 „ 15 --------------------------------+--------+-----------+------------ As a matter of fact, however, the gradient of a macadamised road should not, if possible, exceed 1 in 20,[10] experience having shown that a horse, unless the hill is a very long one, is able to draw his ordinary load for a level up such an inclination, whereas, if it is steeper he is sometimes stopped altogether, even though the carter tries the zigzag route so as to obtain an artificial ease of gradient. The table given in ‘Molesworth’ upon the same subject is too well known to be repeated, and another table may be found in Sir Henry Parnell’s work on roads, which gives a comparison between the draught necessary on a well-paved road at 2, on a well-made, clean macadamised road at 5, whereas on a wet and muddy gravel or flint road it rises to 32! Mr. T. D. Hope, of Liverpool, assuming the power of traction at 100, gives the following table:-- Weight drawn. Level macadamised road 27 cwt. „ granite pavement 30·5 „ „ wood „ 54·75 „ And Lieut. Crompton has given the resistance of wheels in lbs. per ton on different surfaces as follows:-- Very good pavement 35 lbs. Good macadam 60 „ Ordinary ditto 90 „ Newly-laid gravel 200 „ Soft grass land 300 „ Newly-laid metal 440 „ Here “newly-laid metal” comes out very badly, and points to the necessity of rolling, of which I shall speak in a future chapter.