376 Agricultural Experiment Station, Ithaca, N. Y. 



9. It is necessary to exercise greater care in grading pipes for 

 water heating than for steam heating. With steam, a satisfactory 

 fall towards the boiler is much more important than the manner of 

 laying the pipes. 



In the winter of 1893-4'a third series of tests was made. There 

 were two objects in view : to again compare water and steam, and 

 to determine the effect of different pressures upon the water system^ 

 by using high and low expansion tanks. The house and heater 

 were the same as those used in the second test (Bulletin 55), — a 



67.— Experimental Heating Apparatus. 



lean-to lettuce house 16x27 ft., and a Novelty Hot Water Circulator 

 furnished by the Model Heating Co., Philadelphia. Fig. 67 shows 

 the apparatus set up. Three 1^ inch risers or flow pipes run just 

 under the roof, all uniting into one return. A delicate thermome- 

 ter was let into each riser at the farther end (Nos. 2, 3, 4), and one 

 into the return (No. 5) near the heater. Another was inserted in 

 the riser (No. 1) just above the heater. These recorded the inside 



