+ 
the examinations made so far, the authors strongly advise against 
the use of drills of any kind. The appearance of these is much more 
misleading than that of ducks, and it seems impossible to estimate 
their comparative tightness except by tests with special apparatus. 
Our experience up to the present time leads us to recommend closely 
woven duck weighing 8 ounces per yard, when 284 or 29 inches wide, 
or about 10 ounces per yard when the material is 36 inches wide. 
The more expensive grades of cloth are not always the most nearly 
gastight. In the case of two leading concerns which have supplied 
large orders of tents for use in Florida, the medium grades of mate- 
rial, as shown by the prices quoted, have been found to be superior 
in gas-holding qualities to either the cheapest or the most expensive 
of the three grades upon which prices were quoted. 
The form of cover which is at present almost exclusively employed 
is the flat octagon. Frequently those who have never seen a tent of 
this kind fail to realize its simplicity. A square piece of canvas 
would answer the purpose as well as the octagon, but to save material 
and the handling of extra cloth the corners of the square are left off. 
A perfectly circular cover would be more economical in respect to the 
amount of cloth required, but the saving would not cover the extra 
expense of construction in this form. 
For specifications tentmakers may be referred to Bulletin 76 of 
this bureau.¢ In general these specifications are simply that the 
form is approximately octagonal, of any desired size, made of par- 
allel strips of goods overlapped three-eighths or one-half inch, 
double stitched, and all raw edges hemmed. In the case of tents 
50 feet or more in size a reinforcement is desirable across the middle 
section near each end, as described in the bulletin referred to. It is 
desirable that allowances be made for shrinkage, otherwise a tent 
after becoming wet and later drying may not be sufficiently large to 
cover trees of the size for which it was intended. The following 
published statement by the senior author is of importance in this 
connection and is quoted in full: 
Shrinkage of the goods after being thoroughly wet is an important consideration in 
the economical construction of fumigating tents. In order that the tents approxi- 
mate a regular octagon, after having been used for fumigating purposes, it is necessary 
either to have the goods thoroughly shrunk before cutting or to make allowance for 
subsequent shrinkage by cutting the strips longer. A test made with a brand of 
8-ounce duck commonly used in California for fumigating tents showed that the shrink- 
age lengthwise of the goods amounted to 7.5 per cent and crosswise 0.9 per cent. 
This means that in a 50-foot tent the shrinkage would result in the full-length strips 
shortening 3} feet, while the tent would shrink less than 6 inches crosswise of the strips. 
Such irregularities might be remedied by a skirt of 64-ounce drill, but it is simpler to 
~ 
«For sale by the Superintendent of Documents, Government Printing Office, 
Washington, D. ©. .Price, 15 cents. 
b Bul. 76, Bur. Ent., U.S. Dept. Agr., pp. 17-18. 
[Cir. 111] 
