Steam and Hot Water for Greenhouse Heating. 173 



Steam: 



Eiser a b, average for tlie whole time, 211 degrees. 



Eiser A, average for the whole time, 193 degrees. 



Eiser B, average for the whole time, 183 degrees, plus. 



Eeturn a b, average for the whole time, 160 degrees. 



Eiser c d, average for the whole time (208) 212 degrees. 



Eiser C, average for the whole time (191) 196 degrees, pins. 



Eiser D, average for the whole time (185) 192 degrees. 



Eeturn c d, average for the whole time (131), 130 degrees. 

 Hot water: 



Eiser f, average for the whole time, 155 degrees, plus. 



Eiser E, average for the whole time, 137 degrees. 



Eiser F, average for the whole time, 124 degrees. 



Upper return f, average for the whole time, 122 degrees. 



Lower return f, average for the whole time, 111 degrees. 



These figures show that the average temperature of the steam 

 pipes, during six weeks of midwinter, was much higher than that 

 of hot-water pipes. We must now endeavor to ascertain how 

 much of this greater heat was eificient in heating the houses!, 

 how it was related to the practical care and management of the 

 establishment, and how much it cost. 



2. Eadiation from the pipes. — It is necessary at the outset to 

 find out how much of the interior heat in the pipes — in both sys- 

 tems — passes into the atmosphere of the houses as warmth. This 

 is done by a study of outside and inside pipe temperatures, after 

 the method already explained. The methods of obtaining the 

 outside pipe temperatures are necessarily somewhat questionable. 

 If the thermometer bulbs were simply placed against the pipes 

 without being covered, the readings would be very much subject 

 to fluctuation from the effect of air temperatures, and they are 

 doubtless somewhat so by the present method. It is probable, 

 however, that on the whole they give a reasonably fair measure 

 of the heat given off at those points. In order to determine as 

 nearly as possible the relation between the inside temperatures 

 and those obtained on the outside, a thermometer was placed on 

 the outside, at the point where the riser themometer c d was 

 inserted in the pipe, and two on the hot water riser near the point 



