68 IRRIGATION. 



24 to 30 feet long, as wide as the vat, and gradually in- 

 creasing in depth from 3 or 4 feet at the further end, 

 to 6 or 8 inches more at the end connecting with the 

 vat. The excavation should be floored with double boards, 

 with a coating of asphalt or tar between them, and the 

 sides cemented. A coarse grating of stout poles or tim- 



Tbers are laid across this shallow portion of the 

 vat, and is supported in the center by blocks or 

 short posts placed at intervals beneath it. 

 Smaller poles or rails are laid upon these tim- 

 bers not more than 6 or 8 inches apart. 



Upon these poles the manure is piled in a 

 flat heap, made hollow or dishing at the top, 

 so as to collect all the water that may fall upon 

 it. The heap need not be more than five feet 

 high, which is sufficient to cause an active fer- 

 mentation to be kepfc up through the whole of 

 it. The materials of which this heap is com- 

 posed will include every thing of a mineral or 

 organic character useful for manure, that can 

 be procured. Stable manure, straw, marsh hay, 

 weeds, sawdust, peat muck, leaves, woods- 

 earth, night soil, leather scraps, tanner's waste, 

 butcher's offal, lime, ashes, plaster, and bone 

 dust, and the skillful operator will add from 

 time to time such chemical substances as he 

 needs to enrich the compost. There need be 

 Fig. si. no - ear O f losing ammonia by adding lime. The 

 lime is needed for the rapid decomposition of 

 the manure, and the water added every day or two to 

 the heap will seize upon every particle of ammonia 

 formed and carry it into the tank, where it may be 

 fixed by the addition of sulphuric acid or gypsum. 

 The water in the vat should be frequently pumped out 

 for use, and a fresh supply poured upon the heap. A 

 pump that will not readily be choked should be used. 



