CONSTRUCTION OF VENTILATORS AND FLOORS I13 
Ohio, Prof. F. M. Webster has found slats raised 
eight inches or a foot from the ground preferable to 
the ground floor. Where it is intended to drive 
wagons into the house the ground floor will answer 
all purposes. With a slat floor the gas is generated 
beneath, and spreads almost instantly throughout the 
space between the ground and the slats, passes up- 
FIG. 67—DIAGRAM OF GENERATOR AND SECTIONAL VIEW 
OF FUMIGATORIUM. (AFTER WEBSTER) 
ward through the trees, and promptly reaches every 
part of the apartment. 
The generator, shown in Fig. 67, consists of an 
earthen jar of the requisite capacity, a, fixed to the 
end of a plank, 4, and just in front and between two 
posts, cc, through which passes a roller, d, and to 
this last is fixed a pan, e, with back and sides but 
no front, one end of the roller projecting beyond the 
post with a small iron bar or heavy wire, f, passing 
through it, and being fixed and bent at either end, the 
whole having much the appearance of a windlass with 
pan, e, added. ‘The sulphuric acid and water are 
