134 BULLETIN 414, TJ. S. DEPARTMENT OF AGRICULTURE. 
of canvas may be even greater than the three-year period mentioned. 
Tents which are improperly cared for frequently deteriorate rapidly 
from mildew. This usually is the result of rolling and storing the 
canvas while wet, and the best means of preventing it is to dry the 
tentage thoroughly before storing. A number of processes have been 
devised for mildew-proofing, but none has given entire satisfaction. 
The process in most general use consists of immersing the duck for a 
suitable period in a solution of alum and sugar of lead, the propor- 
tions being 4 pounds of each ingredient to one barrel of water. Other 
recipes for this purpose follow: 
1. Dissolve 1 pound of zinc sulphate in 40 gallons of water; add 
1 pound. of washing soda, and when this is dissolved add 2 ounces of 
tartaric acid. Soak* the material 24 hours and allow it to dry without 
wringing. 
2. Dissolve 2 pounds of alum in 7 gallons of hot water. Dissolve 1 
pound of gelatin in 4 gallons of hot water. Mix these two solutions, 
then dissolve 2 pounds of blue vitriol in 1 gallon of hot water and add 
the solution to the mixture of the first two. Soak the duck in the 
resulting mixture 24 horns and allow to dry without wringing. 
CAGES AND CARS. 
Movable convict quarters mounted on wheels, known as cages (or 
lately, in response to a change in public feeling, as cars), have long 
been in common use in the United States, particularly in the South. 
Formerly constructed entirely of wood, they now are also manufac- 
tured wholly of steel by a number of firms. In dimensions they are 
usually 12 or 18 feet in net length and from 7 to 8 feet in width and 
height. 
The cost of a steel cage 18 by 8 by 8 feet is approximately $500, 
which is at the rate of 43.4 cents per cubic foot of space provided. 
By way of comparison, it may be stated that an excellent portable 
building, similar to that described in a succeeding paragraph, can be 
constructed at a cost of not more than 7 cents per cubic foot of space 
provided below the eaves, entirely omitting from consideration the 
additional space between the eaves and the ridge. Such a structure 
should have a life of at least five years. If, therefore, omitthig for 
the present the consideration of the relative porta bihty of the two 
types of quarters, the cage is to equal the portable building in econ- 
omy, it must have a life approximately six times as long, or at least 
30 years. It is not known precisely what life may be expected of 
the cage, for the reason that steel cages have not been in use long 
enough to provide any basis for an estimate; but it is not probable 
that its life will equal the 30-year period which is necessary to place 
it on an economic parity with the portable building. 
