12 BULLETIN 660, U. S. DEPARTMENT OF AGRICULTURE. 
any one of two or more units otherwise would answer equally well, 
the one most familiar and generally used always should be adopted. 
There are many units so closely related to the desired unit of 
measurement that with very little computation they can be trans- 
formed into the desired unit. For example, the knowledge of the 
number of bags or barrels of cement used and the proportion of the 
mixture of the concrete are functions which at once determine the 
amount of sand and stone used. A number of tables giving some of 
the more common and convenient units of measurement used in 
collecting and compiling cost data relating to road work, are given 
in the Appendix. 
