134 BULLETIN 414, U. S. DEPARTMEKT 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 aliun 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 zmc 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 hours 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 pubhc feehng, 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 nimaber 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 hfe of at least five years. If, therefore, omitting for 

 the present the consideration of the relative portability of the two 

 types of quarters, the cage is to equal the portable building in econ- 

 omy, it must have a Hfe 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 Hfe will equal the 30-year period which is necessary to place 

 it on an economic parity with the portable building. 



