V. REGULATORS. 397 



d. Combined isochronal and centrifugal governor. 



e. Model showing T. Silver's earliest attempts at combining centrifugal and 



isochronal principle in his marine governor. 



f. Reversible link motion. 



g. Method of equalising the tension of a spring when in action. 

 h. Marine governor. 



i. Marine governor. 



2000. Model showing the effect of hanging the Arms of a 

 Governor from different points with respect to the axis of rota- 

 tion. Jeremiah Head, M.Inst.C.E. 



By turning the horizontal sheave upon the model with gradually increasing 

 velocity, it will be seen that the crossarmed, or approximately parabolic 

 governor, goes through its range with the least variation of speed. Next in 

 efficiency is that wherein the arms are hung from the central axis, whilst the 

 very common form wherein the arms are hung externally is the least efficient, 

 or, in other words, permits the greatest variation in speed between fully open- 

 ing and fully closing the throttle-valve. 



2001. Drawing, half the actual size, of a Regulator for a 

 25 Horse-power Boiler. M. Cleuet, Paris. 



This appliance is fixed to the inside of the furnace with an inclination of a 

 few centimetres, in such a manner that the plane of the water level proper to- 

 be maintained passes through the upper tube at a point about half its length. 



Connected with the boiler, on one hand, and with the feed pipe on the 

 other, this appliance constitutes a kind of weight thermometer, the expansion 

 and contraction of which depend upon the position of the water level in the 

 boiler, and determine the flow by a discharge of the excess of water injected 

 by the feed pump, which works uninterruptedly. 



495. Back and Snail of Clock, to regulate the number of 

 blows struck each hour. Council of King's College, London. 



496. Model of Chronometer Escapement. 



Council of King's College, London. 



497. Model of Lever Escapement. 



Council of King's College, London* 



498. Model of Horizontal Escapement. 



Council of King's College, London* 



499. Model of Locking Plate of Clock, to regulate the 

 number of blows struck each hour. 



Council of King's College, London. 



2010. Gyrograph. Prof, von Gizycki, Aix-la-Chapelle. 



This instrument serves in investigating the degree of inequality in the 

 velocity of rotation of machine-shafts. The paper drum has rotation and 

 axial velocity. The vertical deflections of the pencil from its lowest position 

 are proportional to the increase of angular velocity of the shaft under exami- 

 nation. The instrument is driven by the latter by means of disc and cord. 



