HEAT-REGULATOR 



795 



Fig. 1145, a, b, is a single thermostatic bar, consisting of two or more bars or rulers 

 of differently expansible solids (of which, in certain cases, wood may be one) : these 

 bars or rulers are firmly riveted or soldered together, face to face. One end of the 

 compound bar is fixed by bolts at a, to the interior of the containing cistern, boiler, 

 or apartment, a I m b, whereof the temperature has to be regulated, and the other end 

 of the compound bar at b is left free to move down towards c, by the flexure which 

 will take place when its temperature is raised. 



The end b, is connected by a link, b d, with a lever d e, which is moved by the 

 flexure into the dotted position b g, causing the turning-valve, air-ventilator, or 

 register, o n, to revolve with a corresponding angular motion, whereby the lever 

 will raise the equipoised slide-damper k i, which is suspended by a link from the 

 end, e, of the lever, e d, into the position k h. Thus a hothouse or a water-bath may 

 have its temperature regulated by the contemporaneous admission of warm, and dis- 

 charge of cold air, or water. 



Fig. 1146, a b c is a thermostatic hoop, immersed horizontally beneath the surface of 

 the water-bath of a still. The hoop is fixed at a, and the two ends b c, are connected 

 by two links b d, c d, with a straight sliding rod d h, to which the hoop will give an 

 endwise motion, when its temperature is altered ; e, is an adjusting screw-nut on the 

 rod d h, for setting the lever/ g, which is fixed on the axis of the turning-valve or 



1145 



1148 



1147 



cock,/at any desired position, so that the valve 

 may be opened or shut at any desired tempera- 

 ture, corresponding to the widening of the points 

 b, c, and the consentaneous retraction of the 

 point d towards the circumference a b c of the 

 hoop, g h, is an arc graduated by a thermometer, after the screw-piece e has been ad- 

 justed. Through a hole at h, the guide-rod passes ; i, is the cold-water cistern ; ifk, the 

 pipe to admit cold water ; I, the overflow pipe, at which the excess of hot water runs off. 

 Fig. 1 147 shows a pair of thermostatic bars, bolted fast together at the ends a. The 

 free ends b, c, are of unequal length, so as to act by the cross links d, f, on the stop- 

 cock e. The links are jointed to the handle of the turning plug of the cock, on oppo- 

 site sides of its centre ; whereby the plug will be turned round in proportion to the 

 widening of the points b, c. h g is the pipe communicating with the stopcock. 



Suppose that for certain purposes in pharmacy, dyeing, or any other chemical art, 

 a water-bath is required to be maintained steadily at a temperature of 150 F. : let 

 the combined thermostatic bars, hinged together at e,f, fig. 1148, be placed in the bath 

 between the outer and inner vessels a, b, c, d, being bolted fast to the inner vessel at 

 g and have their sliding rod k, connected by a link with a lever fixed upon the turn- 

 ing plug of the stopcock i, which introduces cold water from a cistern m, through a 

 pipe m, i, n, into the bottom part of the bath. The length of the link must be so ad- 

 justed that the flexure of the bars, when they are at a temperature of 150, will open 

 the said stopcock, and admit cold water to pass into the bottom of the bath through 

 the pipe i n, whereby hot water will be displaced at the top of the bath through an 

 open overflow-pipe at q. An oil-bath may be regulated on the same plan ; the hot oil 

 overflowing from g, into a refrigeratory worm, from which it may be restored to the 

 cistern m. When a water-bath is heated by the distribution of a tortuous steam-pipe 

 through it, as i n o p, it will be necessary to connect the link of the thermostatic bars 

 with the lever of the turning plug of the steam-cock, or of the throttle valve i, in order 

 that the bars, by their flexure, may shut or open the steam passage more or less, 



