April, '11] DEAN: FATAL TEMPERATURES 151 



(Chart II.) On the second floor the highest temperature, 123.8°, 

 was registered by the thermometer hanging in the open, while the 

 lowest temperature, 98.6°, was registered by a thermometer three and 

 one-half inches in a sack of flour four feet above the floor. (Chart 

 III.) On the third floor the thermometer in the open registered 

 125.6°, and the lowest temperature, 114°, was registered in a flour 

 con.veyor six feet above the floor. (Chart IV.) On the fourth floor 

 the thermometer in the open registered 118.4°, and the lowest tem- 

 perature, 107.6°, was registered by the thermometer two inches in 

 flour in a conveyor near the floor. (Chart V.) 



A hydrograph was placed on the second floor in the middle of 

 the room. The relative humidity of this floor at 10 a. m., or just 

 as the heat was applied was 93 per cent. From 10 a. m. to 12 m. there 

 was a rapid decrease to 40 per cent, and from 12 m. to 5.30 p. m. 

 there was a gradual decrease to 27 per cent. 



Although the temperatures reached were disappointing, and no 

 insects were killed on the first floor, yet on the third floor fully one 

 third of the insects perished, and on the fourth floor about one fourth 

 succumbed to the heat. Even the second floor showed that many 

 insects had perished. The experiment proved the following: More 

 time must be taken to reach the desired temperature; this tempera- 

 ture should be held several hours to allow the heat to penetrate all 

 of the infested parts ; there should be a water trap to draw off the water 

 accumulated in the steam pipes; the steam should be turned on with 

 some pressure so as to heat the mill more rapidly; the steam pipes 

 should be near the floor in order to heat the room. 



In the second experiment, made three weeks later, two changes 

 were made in the heating system. A water trap was attached and 

 arrangement made to turn the steam on directly and with pressure. 

 The arrangement of the pipes in the mill was not altered. At 6 

 a. m., September 11, the mill was shut down and, after the ther- 

 mometers were distributed as in the first experiment, the steam was 

 turned on with ten to twelve pounds pressure. The heat was applied 

 from 6 a. m., until 6 a. m. the day following, and the temperature of 

 the sixteen thermometers noted at intervals of every half hour, save 

 in a few cases when the readings were made at intervals of one hour. 

 The average temperature in the mill at the time the heat was applied 

 was about 90°, and the mean temperature during the day outside of 

 the mill was 77°. 



In nearly all parts of the mill the temperatures gradually increased, 

 and at 3 o'clock p. m. fatal temperatures were reached in several 

 parts. At 6 o'clock p. m. many of the insects had perished. At 9 

 o'clock p. m. fatal temperatures were indicated by nearly all the 



