266 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



sirable for economic transportation or for storage for a great length 

 of time, and necessitates further treatment. Previous to 1875 most 

 of the scrap was sold in a green state, just as it came from the press, 

 but since 1878 practically all of it has been dried or treated with sul- 

 l^huric acid. 



Formerl}^ in drying it was customary at all the factories to spread 

 the green scrap upon platforms, where it was exposed to the action 

 of the sun for several days. While this is the common method at 

 present, most of the large factories have discarded it and are using 

 artificial driers. The platforms are made of tight or matched boards 

 laid flat upon a stout framework or upon the level ground, and are 

 sometimes of large area, covering 2 or 3 acres. The scrap is trans- 

 ferred from the bin beneath the presses by means of screw convej'ors 

 and carried to a receiving bin, where it is dumped into hand carts 

 with caj)acity of one-half ton each and carried to the platform. It is 

 there spread to a depth of from 3 to 6 inches and is frequently turned 

 or raked over, so as to expose all particles to the sun's influence. In 

 threatening weather and when the night dews are heavy, the scrap is 

 raked into windrows or heaps and, if necessary, covered with canvas 

 to protect it from moisture. After two or three days' drying it is piled 

 in heaps and left to sweat for a time, and then is again spread to 

 evaporate the free moisture generated in the heaps. This second dry- 

 ing reduces the amount of moisture in the scrap to about 10 per cent, 

 and the material may be safely bagged and stored for market, though 

 that operation is usually deferred until immediately before its ship- 

 ment. Frequently the dried scrap is ground, especiallj' when it is to 

 be sold direct to the farmers without further treatment, in order that 

 it maj^ be sown in drills with wheat and other grains. 



If good weather could always be depended on, platform-drying would 

 possiblj^ be the most economical and satisfactory method; but OAviug 

 to uncertainties of the weather much difficulty is frequently experi- 

 enced in this process, resulting in a great waste of material and extra 

 expenditure of labor and loss of ammonia in the scrap. This has 

 resulted in the adoi^tion of artificial driers at the largest factories. 

 Several forms of apparatus have been employed, but the princii^le in 

 most of them is similar, the scrap being subjected to a current of 

 heated air by means of a blower. The drier adopted in the largest 

 factories consists of an iron cylinder about 30 feet long and 5 feet in 

 diameter, so mounted as to revolve horizontally. On the interior sur- 

 face are shelves or paddles which, as the cylinder revolves, lift the 

 scrap fed in at one end and permit it to fall to the bottom. A strong 

 current of heated air is forced through the cylinder, extracting the 

 moisture and gradually driving the scrap out at the further end. 



Another form of drier in use consists of a large double cylinder of 

 iron set on an incline, into which the scrap is fed through an opening 

 at the higher end and guided along to the lower end by means of a 

 revolving screw. The space between the inner and outer walls of 



