[Illustration:  Fig. 59.]

[Illustration:  Fig. 60.]

Fig. 60 is an elevation of a boiler with Clark’s Patent Steam and Fire Regulator attached, for the control of the draft of the chimney by the pressure of steam in the boiler.  It consists of a chamber, a, with a flexible diaphragm or cover on top, in communication with the boiler.  On this diaphragm rests a plunger or piston, which is held down like a safety valve, by a lever and weight, b.  The end of the lever is connected with a balanced damper, c, in the chimney.  The weight, b, is placed at any required position on the lever, and when the pressure of steam in the boiler, exerted on the diaphragm, becomes sufficient to raise the weight, the lever rises, and the damper begins to close, and to check the draft in the chimney.  When properly adjusted, the machine works on a variation of from, one to two pounds between the extremes of motion.  When the dampers are very large, say 3 feet or over, they should be set on rollers, like common grindstone rollers; the regulator should be attached directly to the damper, the length of the pipe connecting the regulator with the boiler being of no account.

[Illustration:  Fig. 61.]

Porter’s Patent Governor, fig. 61, is a modification of the ordinary centrifugal governor.  Very small balls are employed, from 2-1/4 to 2-5/8 inches in diameter.  These swing from a single joint at the axis of the spindle, which is the most sensitive arrangement, and make from 300 to 350 revolutions per minute, at which speed their centrifugal force lifts the counterpoise.  The lower arms are jointed to the upper ones at the centres of the balls, and connect with the slide by joints about two inches apart.  The counterpoise may be attached to the slide in any manner; for the sake of elegance, it is put in the form of a vase rising between the arms, its stem forming the slide.  The vase is hollow and filled with lead, and weighs from 60 lbs. to 175 lbs.  It moves freely on the spindle, through nearly twice the vertical distances traversed by the balls, and is capable of rising from 2-1/2 to 3 inches, before its rim will touch the arms.  It is represented in the figure as lifted through about one half of its range of action.

The standard is bored out of the solid, forming a long and perfect bearing for the spindle; the arms and balls are of gun metal, the joint pins of steel; every part of the governor is finished bright, except the bracket carrying the lever, and the square base of the standard, which are painted.  The pulley is from 3 to 10 inches in diameter, and makes in the larger sizes about 125 revolutions, and in the smaller 230 revolutions per minute; the higher speed of the governor being got up by gearing.