THE MONTHLY BULLETIN. 73 



The cost of operation is reduced, the machine saving one man's time. 

 The greatest advantage of this system is in the very material length- 

 ening of the life of the tents. Acid burns in the tents are almost entirely 



eliminated. 



DISADVANTAGES OF THE OWL MACHINE. 



Up to the present time, the most serious disadvantage of the machines 

 is that they were short lived. Their construction has been such that 

 they were unable to withstand the corrosive action of the chemicals used, 

 and all of the eight machines constructed the first year did not survive 

 the season's work. In these first machines, it was noticed that the most 

 serious corrosion occurred on the bottom and along the sides near the 

 bottom of the main generating cylinder. This year's model has been 

 improved by making the lower third of the generating cylinder entirely 

 of lead. Other improvements have been adopted : The development of 

 simpler and more efficient valves and some other details which are not 

 of special interest. So far as known, the machines put out for this 

 season's work are still in operation, although they still have many 

 mechanical faults for correction in the future. One most serious diffi- 

 culty as noticed in the operation of the machines this year is in th,- 

 leakage of the valves due to corrosion. The speaker knows of a number 

 of eastern firms which are producing acid and alkali resistant metals 

 and has furnished the manufacturer with a list of these, and has 

 recently heard that very encouraging results have been obtained experi- 

 menting with some of these new resistant materials. Another point 

 which is in doubt is that the small charges may not be accurately deliv 

 ered by the macliine on account of the fact that the generation is effected 

 within a cylinder of some considerable size. It is believed that thi;-? 

 objection can hold good only for the first or second charge. It has been 

 calculated that one ounce of sodium cyanide will produce hydrocyanic 

 acid gas equivalent to a volume of about four gallons at a temperature 

 of about 80°C. (176°F.). This temperature or higher was found to be 

 maintained during the operation of the machine. According to these 

 figures, it would require approximately ten ounces of cyanide to fill a 

 forty-gallon cylinder completely with gas. For the first charge then 

 for a night's work, it is recommended as a precautionary measure to 

 generate one charge into the air before beginning in order that the 

 machine may be filled with gas. During subsequent operations, it is 

 thought that the machine will be filled with gas and that its delivery 

 will not be affected by the volume of the cylinder. It is to be regretted 

 that this point could not be investigated by the insecticide laboratory, 

 the above remarks being based entirely on theory. It may be that the 

 construction of the Buttress machine offers an advantage over the Owl 

 machine in this respect, owing to the fact that in the former, the genera 

 tion takes place within a small space. While it seems that the machines 

 have given satisfactory service in respect to the destruction of scale, 

 the machines have not been thoroughly tested out on a scientific basis. 

 Unqualified endorsement, therefore, of the fumigation machines can not 

 be given at this time. 



OPINIONS OF THE USERS OF THE MACHINES. 



The limited time at the disposal of the speaker made it impossible to 

 observe the operation of any of the machines except those at the 

 Limoneira Company's ranch at Santa Paula and at the, properties of 



