328 



THE MONTHLY BULLETIN. 



because of the difficulty in reading the small fractions at night and 

 beeanse few scales are made to register these small amounts accu- 

 rately. All less than half ounces are placed in the lower figure, 

 while half ounces or over are placed in the next higher figure. A 

 more convenient way of fixing up the schedule is to have a cylinder 

 made of zinc, with a narrow slot, the width of a row of figures, covered 

 b}^ a glass, and a wooden roller on the inside, similar to a rolling pin. 

 Each end of the cylinder is closed by a cap with a hole in the center, 

 in which turns the handles of the wooden roller. The chart or schedule 

 is attached to the roller so as to revolve in the cylinder. The figures 



Fig. 315. — A water supply wagon for a large fumigating outfit. 



P. C. Jr. Ent.) 



(After Pierce, 



of the distances around are pasted along the top of the slot to conform 

 with the like numbers on the schedule. In finding the dosage one has 

 only to turn the roller until the distance over shows at the left-hand 

 end of the slot, the figure at the top of the slot shows the distance 

 around. In this way, the chart is kept perfectly dry and bright and 

 the possibilities of making a mistake are reduced to a minimum. This 

 arrangement was first invented by Mr. McFadden, who uses it on all 

 of his chemical carts. 



MISCELLANEOUS EQUIPMENT. 



Rubber gloves for handling the acid graduate and generators, pure 

 rubber tubing for drawing off the acid, acid clamps or cut-offs to 

 control the flow, a pair of scales registering ounces, thermometer and 

 good lights are as necessary as any of the other equipment. 



