34 



ing, six by eighteen inches, which is filled with pumice stone moistened 

 with sulphuric acid, and is made so that it can be revolved for the purpose 

 of bringing all particles of the pumice stone in contact with the acid. 

 Through this drier the gas passes onward into pipes, which lead into the 

 tent. Parallel with the pipe, passing toward the drier and connected by 

 an elbow, is a galvanized iron pipe, on top of which is fastened a Gumming 

 fan blower. The blower can be made to act two ways by means of a cii'- 

 cular valve, this being moved by a rod. The blower blows forward through 

 the pipe, which meets the gas which has passed through the drier, driving 

 it into the tent. The object of the valve is to prevent the escape of any 

 gas which has not passed through the drier and which might contain 

 ammonia. The suction pipe of the blower passes directly into the tent, 

 and consequently when the gas is in the tent it is kept circulated when the 

 blower is at work. 



The experiments on orange trees ranging from eight to twelve feet high 

 were made during the months of June and July of 1888, near San Mateo, 

 at the grounds of H. Barroilhet, Esq., who kindly furnished me with 

 assistance in transporting the machinery and putting it up, also in helping 

 to operate the apparatus. Owing to the trees being very near together it 

 was impossible to use horse power in moving the tent, and this made our 

 progress very slow and tedious. Strong winds interfered also, very seri- 

 ously tending to make the tent leak. The tests were made during all 

 kinds of weather, from 60 degrees F. to 85 degrees F., calm and windy, 

 and when the drier was well saturated with acid no harm was done to the 

 tree; young fruit even during a confinement of forty minutes during the 

 noon hour, not being affected. On the other hand, when for the lack of 

 sulphuric acid the drier was not sufficiently charged, serious harm resulted, 

 the foliage in a couple of days falling off. This was especially the case 

 when the operation was done during the middle of the day, but bad effects 

 also resulted when done in the evening as late as 7 p. m. at a temperature 

 of 60 degrees. The effect on the icerya, which were present in immense 

 quantities, was nearly the same when a tree was confined for twenty-five 

 minutes, as when for forty-five minutes, only the bugs themselves and from 

 50 to 75 per cent of the eggs are killed. That the prevailing wind may 

 have had a good deal to do with my failure of doing better at such times 

 is possible, but I am satisfied from general results that when orchards have 

 to be treated on a large scale it will be found necessary to give two treat- 

 ments for extermination, and I should recommend in accordance with this 

 view that these two treatments be given at four-week intervals, which will 

 give an opportunity for remaining eggs to be hatched. 



Cost of Treatment. 



Placing cyanide of potassium at 50 cents a pound and acid at 8 cents, 

 we have the solution of cyanide at a cost of 1 cent, and acid per ounce y^ 

 cents, making it 27^ cents for a twelve-foot-high tree for one treatment. 



On level ground two men and one horse can handle the tent and treat 

 two trees per hour, allowing twenty-five minutes for the dose to act and 

 five minutes for moving and getting ready. One horse, 50 cents; one man, 

 $2; one man, $1 50; total, $4; or an expense of 20 cents per tree. 



If two apparatus are used they can be worked with the same force, mak- 

 ing the expense but half, or 10 cents, apiece when forty trees are being 

 treated once, or for two treatments 20 cents each. To this add the cost of 

 material, which would, for a twelve-foot-high tree, be 55 cents. Besides 

 this, there must still be added the price of labor of putting on proper bands. 



