174 Agricultural Experiment Station, Ithaca, N. Y. 



where riser thermometer f was inserted. All the steam risers are 

 painted, while those carrying hot water are not; in order to 

 obtain uniform r(>'sults, a portion of the hot-water pipe here was 

 painted two coats, and one thermometer was placed on this, the 

 other on the unpainted surface. 



The average difference between inside and outside temperatures 

 in the steam riser at times when there was a free circulation w'as 

 about 22 degrees, with an inside temperature of about 214 degrees. 

 The average difference in the hot water pipe where painted was 

 5 9-14 degrees, unpainted 4 1-2 degrees, with an inside tempera- 

 ture in each case of nearly 122. This indicates that painted pipes 

 radiate slightly less heat than unpainted ones. The great differ- 

 ence between the steam and hot water pipes is probably due to 

 the higher temperature and more rapid motion of the steam 

 Consecutive observations on the steam riser made at a timC; 

 when the steam was going down gave the following comparisons: 



Inside temperature, 147 degrees, 130 degrees, 120 degrees, 110| 

 degrees, 100 degrees, 90 degrees. 



Outside temperature, 137 degrees, 122 degrees, 114 degrees, 106 

 degrees, 98 degrees, 89 degrees. 



These figures show that the greater the pressure — or the inside 

 temperature — the greater is the proportionate difference between 

 outside and inside temperatures. The outside temperature may 

 be taken as the radiating or warming power of the pipe, and, 

 whatever difference there may be between the outside and the 

 inside, represents the amount of heat which is carried further 

 on. This greater difference under increasing pressure is due, 

 apj)arently, to the more rapid circulation of the steam at such 

 pressure by which proportionally less is given off at any one 

 point, it being distributed over a greater length of pipe. Thisi 

 rapid movement is, therefore, an important advantage which 

 steam possesses over hot water for heating long houses. 



The veiy few other observations obtained on the steam riser at 

 low temperature indicates that this relation between outside and 

 inside temperatures is reasonably uniform. The range of inside 

 temperatures from which comparisons were obtained in the hot 



