54 ROYAL SOCIETY OF CANADA 



special balance designed by Prof. Bovey to weigb tbe force of impact. 

 Tbis balance is used in connection witb tbe jet from tbe tank. It sliould 

 be mentioned, bowever, tbat a stand-})i]ie, witb fittings for various ori- 

 fices and nozzles, is connected witb tbe bigb-level reservoir of tbe city, 

 and is also arranged to be used in conjunction witb tbe impact balance. 

 By tbis means experiments can be made under heads ranging up to 

 •280 feet. As tbe results derived from tbis arrangement are not easily 

 comparable with those obtained from tbe tank, no observations were 

 made in tbis series with beads higher than those which could be obtained 

 with the tank. 



Tbe impact balance consists of a yard-arm or beam, 4 feet long, sup- 

 ported at tbe centre on a pair of knife-edges. At each end of tbe arm, 

 supported on knife-edges, are two buckets, each capable of holding about 

 20 pounds of water. There is a vertical arm attached to tbis horizontal 

 arm ; tbis vertical arm has a vertical slot in it in which a rod can be 

 fitted and seciired. This rod is graduated in inches and decimal parts, 

 so that it can be adjusted vertically to any desired height. 



This rod has at its lower end a circular slot, in which tbe piece which 

 holds the vanes or buckets slides, and can be adjusted at any required 

 angle b}' means of graduations in degrees. Tbis })iece was so designed 

 that the centre of tbe bucket or point where tbe water strikes is coinci- 

 dent witb tbe centre of tbe circular slot, so tbat tbe adjustment of tbe 

 angle of the slot does not affect the height of tbat point as determined by 

 tbe vertical adjustment. Thus tbe two adjustments are rendered per- 

 fectly independent. 



The frame on which are the two knife-edges on which tbe balance is 

 carried is capable of a horizontal longitudinal motion in tbe direction of 

 tbe path of the jet. A strong cast iron bracket is fastened at one end to 

 the side of the tank above the orifice, and tbe other is supported by a tie- 

 rod attached to a beam above. Tbe bracket has a plane straight guide, 

 which is set horizontal, and on which the frame slides. The bracket is 

 jtrovided with graduations in feet, so tbat tbe frame, and consequently the 

 centre of the bucket, can be set at any desired distance from tbe orifice. 



It was necessary previously to determine the deflection of tbe jet at 

 the ])ai-ticular distances at which it was proposed to observe tbe force of 

 im])act. and to calculate tbe angle of inclination of the path to tbe hori- 

 zontal. Then the vane bad to be set vertically, so tbat the jet might 

 strike it in tbe centre; and also at tbe correct angle, so that it might 

 receive tbe jet .><ym met ri call}'. 



Tbe arm of the balance was providt-d witb a pointer at one end, so 

 tbat tilt-' balance might be always balanced in tbe same position, indi- 

 cated by a mark on a scale on the frame, in which position tbe centre of 

 the bucket is vertically below tbe knife-edges on which tbe arm is sup- 

 ])orted. 



