152 DESTRUCTIVE INSECTS OF VICTORIA: 



air-tight iron covering, having an opening on one side of the fan-wheel^ 

 through which the air is drav^^n out of the tent by means of a tin pipe, 

 the base of which covers this opening. In tlie lower part of the fan- 

 wheel chamber is a large opening, placed opposite to a similar opening in. 

 one side of an iron pipe closed at one end while to the other end is attached 

 the tin pipe through which the air is to be forced into the tent. When, 

 the crank operating the fan-wheel is turned the air is drawn out of the 

 tent through the tin pipe, and passes into the fan -wheel chamber through 

 the hole in the side of the latter, and by the rapidly revolving fan- 

 wheel is thrown by centrifugal force into the tent. 



I had a blower constructed upon nearly the same principle as the 

 above, except that the fans were made of tin, as was also the covering 

 of the fan-wheel chamber, but it did not give very good satisfaction. 



There is a machine manufactured at San Jose, Cal., and known as 

 the Acme fumigator, which is provided with an iron fan-wheel driven 

 by a belt. The blower of this fumigator is much too small to be used 

 for agitating the air in the tent, but the manufacturer, Mr. A. R. Tomkin^ 

 informs me that they could be made of almost any size, and that the 

 price would be less than a third of that of the Cummin's blower. This 

 is a very simple arrangement, and if made large enough would doubtless 

 answer the purpose quite as well as the Cummin's blower, and at a 

 much lower price. 



It has also been suggested to use a common blacksmith^s bellows for 

 the purpose of stirring the air in the tent, but it would appear to be a 

 difficult task to manipulate it in such a way that the air would be drawn 

 out of the tent as well as forced into it. 



In the Culver tent a wooden fan is at present used, being placed 

 inside of the tent ; a fan of this kind, however, will always cause more 

 or less trouble on account of its striking the branches of the tree 

 inclosed by the tent. On this account it is advisable to always 

 have the apparatus for agitating the air in the tent placed on the outside 

 of the latter. 



Whatever form of apparatus is used, it should be placed as near as 

 possible to the point where the gas is to enter the tent ; and if it can 

 be so arranged that the gas can pass into the tent by the same pipe 

 through which the air is forced into the tent, this will be a great 

 advantage, since the gas will then become more thoroughly mixed with 

 the air in the tent before reaching the foliage. 



There are doubtless many valuable insecticides other than those in 

 general use, and these will, if thought necessary, be included in 

 Part II. of the Handbook. 



