two pairs of flour stones, one dressing machine, two pairs of stones grinding oatmeal, and one pair of shelling stones.  The flour stones, one pair of the oatmeal stones, and shelling stones, are 4 feet 8 inches diameter.  The diameter of the other pair of oatmeal stones is 3 feet 8 inches.  The length of the cylinder of the dressing machine is 7 feet 6 inches.  The flour stones make 87 revolutions in the minute, and the larger oatmeal stone 111 revolutions, but the smaller oatmeal stone and the shelling stone revolve faster than this.  At the time the indicator diagram was taken, each pair of flour stones was grinding at the rate of 5 bushels an hour; each pair of oatmeal stones about 24 bushels an hour; and the shelling stones were shelling at the rate of about 54 bushels an hour.  The fanners and screen were also in operation.

696. Q.—­Have you any other case to enumerate?

A.—­I may mention one in which the power of the same engine was increased by giving it a larger supply of steam.  The engine when working with 8.65 horses power, gives motion to one pair of oatmeal stones of 4 feet 6 inches diameter, and one pair of flour stones 4 feet 8 inches diameter.  The oatmeal stone makes 100 revolutions in the minute, and the flour stone 89.  The oatmeal stones grind about 36 bushels in the hour, and the flour stones 5 bushels in the hour.  The engine when working to 12 horses power drives one pair of flour stones, 4 feet 8 inches diameter, at 89 revolutions per minute and one pair of stones of the same diameter at 105 revolutions, grinding beans for cattle.  The flour mill stones with this proportion of power, being more largely fed, ground 6 bushels per hour, and the other stones also ground 6 bushels per hour.  When the power was increased to 18 horses, and the engine was burdened in addition with a dressing machine having a cylinder of 19 inches diameter, the speed of the flour stone fell to 85, and of the beans stone to 100 revolutions per minute, and the yield was also reduced.  The dressing machine dressed 24 bushels per hour.

697. Q.—­What is the power necessary to work a sugar mill such as is used to press the juice from canes in the West Indies?

A.—­Twenty horses power will work a sugar mill having rollers about 5 feet long and 28 inches diameter; the rollers making 2-1/3 turns in a minute.  If the rollers be 26 inches diameter and 4-1/2 feet long, 18 horses power will suffice to work them at the same speed, and 16 horses power if the length be reduced to 3 feet 8 inches. 12 horses power will be required to work a sugar mill with rollers 24 inches diameter and 4 feet 2 inches long; and 10 horses power will suffice if the rollers be 3 feet 10 inches long and 23 inches diameter.  The speed of the surface of sugar mill rollers should not be greater than 16 feet per minute, to allow time for the canes to part with their juice.  In the old mills the speed was invariably too great.  The quantity of juice expressed will not be increased by increasing the speed of the rollers, but more of the juice will pass away in the begass or woody refuse of the cane.