60 FLY CONTROL. 
as the irritation to eyes, nose, and throat is severe. After entering 
the room, the flies should be at once swept up and burned, to avoid 
the possible chance of any reviving. 
Another substance which gave as good results as the formal- 
dehyde is phenol-camphor, a compound used to kill mosquitoes in 
the yellow-fever outbreak in New Orleans a few years ago. It is 
far less offensive to the user than formaldehyde, but a little more 
trouble to prepare. Its preparation is as follows: 
It consists of equal parts of carbolic acid crystals and camphor 
gum. The carbolic acid crystals can be liquified by heat, and 
then poured over the camphor gum. When moderately heated, 
this mixture gives off dense fumes which rapidly diffuse. They 
soon condense and settle on all exposed surfaces as a light mois- 
ture. The effect of these fumes upon flies is somewhat the same 
as that of pyrethrum but more certain in its effects. The flies, 
however, should be swept up afterward and destroyed. The fumes 
are irritating and produce symptoms of phenol poisoning in some 
people. This camphor-phenol mixture has an advantage over 
pyrethrum in the material being less in bulk and the rooms may 
be entered after an hour, thus enabling one to make a quicker ap- 
plication. Four ounces of this mixture should be used to every 
thousand cubic feet of space and the exposure should be for two 
hours to secure best results, after which time, doors and windows 
may be opened. Not more than eight or ten ounces of the cam- 
phor-phenol should be placed in a basin, preferably an agate wash 
basin. It is vaporized by heat and can be placed over a lamp or 
other flame, at such a height as to volatilize rapidly but not over- 
heat the dish and cause the contents to take fire. If a small 
alcohol lamp is used, the basin should be placed over a piece of 
stove pipe which has been so cut as to form legs at the bottom 
and to bring the basin ten inches above the flame. Punch a series 
of holes just below the top of the pipe to provide a draft. 
Chlorine gas generated by pouring sulphuric acid over chloride 
of lime gave excellent results. We used four ounces of lime for 
each 1.000 cubic feet of room space; five ounces would be better. 
To each ounce of chloride of lime was added two fluid ounces of 
sulphuric acid. This was done in an enamelled pan. - Owing to 
the dangerous nature of chlorine gas, however, we do not feel 
like recommending it as a fumigant except for those who are 
familiar with the handling of chemicals. 
Experiments with the use of carbolic acid, creosol, sulphur and 
pyrethrum did not give satisfactory results. 
