February, '10] HINDS AND turner: carbon DI-SULFID 51 



other merely passes through the stopper. A similar arrangement is 

 provided for another bottle containing the carbon di-sulfid liquid. 

 On one of the two lines connecting the bell jar and the liquid recep- 

 tacle, a rubber bulb is inserted, which should be provided with valves 

 so that all air passing through it will be propelled in one direction. 

 By working this bulb a few minutes with the valves open, a saturated 

 atmosphere may be easily obtained at any temperature and the amount 

 of liquid per thousand cubic feet determined if desired. The valves 

 may then be closed and connection made with another bell jar of sim- 

 ilar size, and so that in a similar manner the atmosphere charged with 

 bi-sulfid may be divided between the two jars. This gives an atmos- 

 phere of one-half saturation, and further division may be made in this 

 manner. Working in this general way, it has been determined that 

 one fourth or one eighth of a saturated atmosphere may be very nearly 

 as quickly effective in destroying weevils as is the full strength, but 

 in either case the question of temperature seems to be equally impor- 

 tant. In any case, it is certain that the killing strength of the gas 

 for the rice weevil must be maintained for at least one hour. If fur- 

 ther dilution is used, the length of the exposure must be increased to 

 secure death. 



In order to test the effect of various strengths of treatment upon a 

 larger scale, we have constructed a fumigation box to facilitate the 

 work. One of these boxes is so arranged that 25, 50 or 75 cubic feet 

 capacity may be utilized. The boxes are so made as to be practically 

 gas-tight, and the doors fitted with double bearings which are thor- 

 oughly felted. The doors are entirely removable and fastened in 

 place by six refrigerator bars each. The liquid di-sulfid is introduced 

 through the top of the box by a graduated burette, the dosage quanti- 

 ties being determined in cubic centimeters instead of fractions of an 

 ounce. Arrangement is made for ventilation by a line of three-inch 

 piping connected with a blacksmith's forge fan, and with similar exit 

 pipes through which the gas from any section of the box may be 

 quickly driven out of doors upon the conclusion of the experiment. 

 The openings to these pipes are tightly closed by conical plugs cov- 

 ered with felt. The appearance of the boxes and the method of their 

 use is shown in the accompanying illustrations- (PI. 5, figs. 3, 4). These 

 fumigation boxes have greatly facilitated the application in various 

 tests, but the amount of labor involved in determining the effect, par- 

 ticularly upon immature stages, has been very great. 



As indicating the nature of the results obtained in this work, the 

 following table has-been prepared: 



