The transport of clay by means of wheelbarrows is certainly the most onerous method. In all cases where it is possible to do so, a portable tramway should be substituted for them. These tramways (the best-known type of which is the Decauville) are now comparatively cheap. (The 40 centimetre gauge costs 3 fr. 10 c. per metre, and the 50 centimetre gauge 3 fr. 20 c).

Fig. 9. Earthwork Waggon.

For man traction, which is the simpler method if the distance is not too great, a waggon is used containing 250 litres for the 40 cm. gauge or 300 litres for the 50 cm. gauge, making the volume of about five or six wheelbarrows.

The waggon is emptied very simply by tipping it over on one side as shown in Fig. 10. These waggons, which are made entirely of iron, cost about 100 francs (1897).

## B. Horse Traction

If the distance from the place of extraction to the manufactory is somewhat great, and if the clay is worked on a slope, it is politic to use horse traction. Waggons like that in Fig. 11 are then used, furnished with a central buffer and couplings. The waggons contain 500 litres. A number of them, varying according to the inclination of the line and the strength of the horse, are coupled together. The horse soon gets accustomed to his work. It is well to make it easier for him by adopting a special (Fig. 13) harness, which permits him to develop the maximum of power. The swing-bar (Fig. 12)shown at the left of the figure is furnished with a leather cover to the coupling to prevent the horse's tail from being caught in it.

For the information of our readers we will calculate the net cost per cubic metre of the extraction of the clay and its transport over a certain distance by man and horse traction. This cost is evidently variable, depending upon the price of labour and the difficulty of extraction. We will assume an ordinary clay easily dug and loaded.

## Net Cost Per Cubic Metre Of The Extraction Of Clay And Its Transport By Waggon

This net cost is made up of three parts:one fixed, i.e. the cost of extraction, the two others varying according to the distance, and including the cost of traction, depreciation, repairs, maintenance, and interest on capital. We will estimate them in turn.

Fig. 10. Earthwork Waggo.

Fig. 11. Earthwork Waggon with Central Buffer.

Fig. 12. Whipple-tree with Coupling cover. Fig. 13 Horse with Special Set of Haruess for Waggon Traction.