represented in Figs. 14, 15, 16 and 17. In general they all consist of a revolving disc placed in a horizontal position, and provided with swinging pockets,

in which the test-bottles are placed. When at rest, the pockets hang down, permitting the bottles to stand upright. When the disc is in motion the pockets swing out, carrying the bottles to a horizontal position, the necks of the bottles being directed in toward the center. The testers should be made to carry an even number of bottles. The steam-turbine tester is the best form of centrifugal for factory work. It has the advantage of maintaining a uniform rate of specd and, in addition, the contents of the bottles are kept hot, and hot water is supplied. In some forms, in which the exhaust steam is not carried away and in

represented in Figs. 14, 15, 16 and 17. they all consist of a revolving disc placed= zontal position, and provided with swing

which no dampers are provided in the cover, the steam testers may heat the fat too high. For use on farms, hand-testers are available. It is always necessary that

Capable of unusually high speed--safe, accurate and convenient. Made by International Instrument Co. Cambridge, Mass.

the tester should be securely fastened to a firm foundation and so set that the revolving disc is level. The centrifugal should run smoothly, without jar or tremble, when going at full speed.

Estimating speed of centrifugal tester.-In order to cause separation of the most fat possible, the centrifugal disc must move at a sufficient speed. The required number of revolutions depends upon the diameter of the disc, to the edge of which the test-bottles are

attached. The smaller the wheel, the greater must be the number of revolutions a minute.

Farrington and Woll have prepared the following able, showing the necessary number of revolutions for different sizes of testers:

In the case of steam-turbine testers, they arc, or should be, made to run at the desired speed under a definite head of steam. These testers should always be provided with a pressure-gage, and a speed-indicator is also desirable.

In the case of hand-testers, the speed can be ascertained in the following manner: Give the handle one full turn and count the number of times a given point on the disc goes round. Suppose, for example, that the diameter of the disc is 16 inches and that it revolves 14 times for one turn of the handle. Such a disc ought to revolve 848 times per minute according to the preceding table. The handle must be turned around as many times a minute as 14 is contained in 848 in order to attain the desired speed, which is found to be about 60 times, or once a second. Then, with watch in hand, regulate the turning of the handle until it