THE IMPLEMENTS OF THE FARM. 20 



feed-water tank of the boiler. In either case it should 

 have a feed-water pump and feed-water heater for supply- 

 ing the boiler. A Cornish or Galloway boiler should be 

 well stayed and fitted with manhole and mudhole covers, 

 check valve, two safety valves, blow off cock, gauge taps, 

 glass water gauge, steam pressure gauge, firing tools, 

 oil feeder, and complete set of wrenches, screw hammer, 

 and spare gauge glasses. Compound engines, universally 

 used in other arts, are now also at work in agriculture. 



Traction engines are preferable to portable, as they move 

 themselves from place to place, hauling after them thresh- 

 ing machines and other driven machinery, with water carts, 

 waggons, sleeping vans, that may be required. Thus, by 

 attaching winding drums to them they may be used for 

 ploughing and cultivating land, as already noticed ; also 

 for hoisting in quarries, mines, &c. Springs are being 

 applied on the wheels by several makers. Improvements 

 in the manufacture of steel allow it to be substituted for 

 iron with advantage, as it is lighter, stronger, and more 

 durable. Vertical boilers, as Paxman's, have a number of 

 water tubes, which curve up through the fire-box, termi- 

 nating in the steam chamber, each tube having a deflector 

 on the top to prevent spray. The Cochrane vertical boiler 

 has horizontal tubes. 



Horse Gears are of two kinds : high and low. In the 

 former, generally known as "the horse mill course," the 

 gearing is above the circular path in which the horses work, 

 the large wheel which drives the lay shaft being supported 

 on a vertical shaft. In the low class, by far the most 

 numerous, the driving gear is on the ground, the horses 

 stepping over the lay shaft as they move round in a circular 

 path. 



