62 
were covered with water after a slight shower we found that they were 
badly injured by this strength, though we doubt they would have been 
hurt had they been dry. Possibly a less time may be sufficient, but 
we doubt that in handling fifty or one hundred covers it would be of 
much advantage, as they could hardly be changed and the gas gen 
erated in less time. The very much larger amount of gas than is 
necessary in a larger box or frame is due to the relatively large soil 
surface, and the fact that more or less necessarily leaks out around the 
edges at the bottom. In using these covers for such insects as melon 
lice it would rarely be necessary to fumigate every hill. But were 
every hill fumigated, with hills 5 by 5 feet, the chemicals for the 
treatment would cost not over 75 cents per acre, and with one hun- 
dred covers two men should be able to fumigate 3 to 5 acres a day. 
Upon the first opportunity we shall try this treatment with fifty or one 
hundred covers over an acre or two during the present season. 
The fumigation of plants grown in rows is, however, more difficult, 
and presents some obstacles. A frame 15 feet long, with two sides 
slanting so that in cross-section the frame was triangular, 20 inches 
wide at the open bottom and 8 inches high, was first used, but it was 
soon found, as had been expected, that the gas would not diffuse 
readily in such a shaped covering. 
It seemed desirable, therefore, to determine the exact manner of 
diffusion of the gas in such an elongated frame, and also points as 
regards (1) the amount of gas produced by a given amount of KCn, 
sulphuric acid, and water, (2) the influence of the soil and wet plants 
upon the strength of the gas, and (8) whether the strength of the gas 
deteriorates after a given time. This work was taken up by the station 
chemist, Mr. C. L. Penny, who has very carefully secured and ana- 
lyzed samples of the gas under various conditions to determine these 
points. Only a mere summary of the results can now be given. Dur- 
ing the present summer we purpose studying the manner of diffusion 
of the gas in a room such as nurserymen use as a fumigatorium, and 
later will publish a detailed account of all the experiments. 
A frame covered with rawhide paper, 13% feet long and 18 inches 
square at the ends, was constructed for this work. The bottom was 
taken off and the frame aired after each test, and sealed with putty when 
replaced. The gas was generated by running the acid into the cyanide 
solution by means of a stopcock so that there was no possibility of loss 
or leakage. A known amount ‘of gas was drawn ofif—after passing 
through a drying tube—into several large bottles, by first exhausting 
these with an air pump. A 36-gallon kitchen hot-water boiler was 
nearly exhausted of air, and a mercury gauge attached. Between this 
and the reservoir of bottles was placed a train of wash bottles contain- 
ing nitrate of silver solution, and all were then connected. Upon 
opening a valve the larger tank thus drew a quantity of the gas through 
the wash bottles whose volume was easily determined by the mercury 
