



THE WEIGHING OF MARKET HAY. 97 
should be tested frequently and balanced daily, or even oftener, if 
weather or other conditions make more frequent balancings necessary. 
At some warehouses scales are so placed that the car remains upon 
them while it is being loaded or unloaded; at others they are placed 
so that cars are moved over them when being switched to and from 
the warehouse. There is no material difference as to which location 
is used, but care must be taken to see that the car contains the same 
equipment when being weighed loaded and empty. 
ACCURACY OF WEIGHTS. 
All things considered, weights obtained on track scales in proper 
condition and located under cover are subject to fewer chances for 
error than weights obtained by any other method. The load is 
weighed in one draft, which overcomes the danger of omitting the 

I'ig. 8.—Broken bales, showing how losses may occur in terminal markets. 
weights of any draft, as is possible when weighing on platform or 
wagon scales. 
The tare is also obtained in one draft, frequently without any 
movement of the car from the time the gross weight was obtained, 
so that about the only chance of error is in tabulating the weight. 
Tf a registering beam is used, this chance of error also is eliminated. 
Because of the great cost of track scales, however, and the fact 
that their use would be confined in most cases to one warehouse, they 
are frequently impracticable and generally can not be maintained, 
except by railroads or large concerns. 
CERTIFICATES FOR TRACK SCALE WEIGHTS. 
Certificates of weights for track scales should differ but lttle from 
other weight certificates, but since the weight is obtained in one 
