MILLS AND OTHER BUILDINGS 175 
taboratory, with cockroaches, the so-called ‘‘ silver 
fish,’’ and the Angoumois grain moth. C. P. Hartley, 
an assistant in the laboratory, had the building fumi- 
gated with very excellent results. At the snggestion 
of Dr. Webber the following statement of facts was 
furnished by Mr. Hartley : 
‘‘During the summer of rgor one of the laboratories 
of the United States Department of Agriculture became 
badly infested with mice and insects of many kinds. 
It was decided to try the efficacy of hydrocyanic acid 
gas in ridding the building of these pests. This labora- 
tory had become the abode of cockroaches, beetles, 
crickets, moths, flies, etc., to some extent because it 
was connected with greenhouses where these insects 
abounded, but more especially because of seeds, fruits, 
and plant specimens that were stored in the various 
rooms. ‘The entire building, a two-story frame struc- 
ture of eight rooms, was twice fumigated during the 
latter part of the summer with such success that the 
building was free from inse¢ts for the rest of the year. 
The first fumigation was given the latter part of 
August and freed the building for a week or more, 
after which time many small roaches and other young 
insects became noticeable which probably developed 
from eggs in the building. 
‘‘For the first fumigation old stock potassium 
cyanide from several sources and of various appear- 
ances was used, but for the second, ten days later, 
fresh material was used, and resulted in killing every 
insect and mouse in the building. This fumigation 
was started at four o’clock in the evening and the 
building was kept closed until the next morning, when 
