_Excavation._—The cost of excavation depends on the character of the material and on the amount of water present, the cost of pumping or bailing the latter, if in large quantity, adding materially to the cost of shovelling. The material through which the trenches are driven may vary from a sand which can be shovelled without loosening, to solid rock which must be blasted, an intermediate condition of soil being known as hardpan and its excavation costing nearly as much time and effort as rock itself. If the soil is sand, into which a shovel or spade can be pushed without any picking of the material, the cost, as already stated, will be about fifteen cents a cubic yard for shovelling, and if the excavation is in trench and not more than six feet deep, the entire trench can be excavated for seven and a half cents a lineal foot. It is very unusual, however, to have conditions so favorable that such a low price can be counted on. If the material requires picking, instead of fifteen cents a cubic yard it will cost thirty cents a cubic yard, and a trench two feet wide and six feet deep will cost fifteen cents a running foot instead of seven and a half cents. If care is not taken at the start to throw the dirt well back, it will be necessary to re-handle the dirt from the bottom of the trench, throwing it back on the pile, and this will add from five to ten cents a cubic yard, depending on what proportion of the entire excavation has to be re-handled. In the excavation for a tank, it is quite possible that the entire material may have to be re-handled and the cost thus be increased by fifteen cents a cubic yard. If the ground is very hard, as when boulders and clay are intermixed, it may require twice as much time for loosening as for shovelling, in which case the cost of digging the trench will be forty-five cents a cubic yard, or twenty-two and a half cents per lineal foot, with five or ten cents added if the material has to be re-handled. If the material is a loose sand or gravel, the trench will probably require sheeting, that is, boards or planks on each side of the open trench with braces between, in order to prevent caving of the banks. If new lumber has to be purchased for this purpose and its cost added to the cost of excavation, an additional sum per cubic yard or per lineal foot will be added, somewhat in proportion to the total amount of excavation to be done. Finally, if the soil through which the trench is being dug contains water, it may be necessary to have one or two men continuously pumping during all the time that the excavation is going on, and this also will add to the cost per cubic yard or per lineal foot of the trench.