The tables as found in the article are have been designed to provide concrete contractors with as much data as can be gathered on the type and size vibrator to use for a particular job. Based on these table, a contractor should be able to select the number of vibrators to use for a job in addition to determining whether an electric or pneumatic or a gasoline-driven unit would serve his purpose best. Let's say, for example, that you are placing concrete for a large foundation and you want to know: (1) what type vibrator will work best; (2) what horsepower and head size are most suitable for the job; (3) how long it will take to vibrate the concrete if 2 and one-half inch slump is specified; and (4) how many vibrators will be needed to do the job in the shortest possible time. Table one shows that for a large foundation you could use a 2 horsepower electric vibrator. Table 2 shows that this vibrator will vibrate approximately 9 cubic yards of 2 and one-half inch slump in an hour. Table 3 shows the diameter of vibration on the basis of aggregate size.