153 . REPORT — 1870. 



ment and registration are effected with reference to each and every stroke 

 of the engine, and furnish a means whereby a correct judgment may be 

 formed as to whether there has at any time been a want of due observance 

 of economy in the use of fuel, or whereby the comparative merits of dif- 

 ferent kinds of fuel or of lubricants may be tested. In cases where power is 

 supplied to tenants, this instrument furnishes the only means whereby the 

 power so sujjplied may be accurately measured. And in the case of marine 

 engines, in a rough sea it is the only instrument that can give any reliable 

 information as to the power exerted by the steam-engines, inasmuch as it is 

 frequently impossible to obtain consistent diagrams by the ordinary indicator 

 during a whole voyage across the Atlantic. The steam-power meter and 

 continuous indicator, as its name implies, shows at all times the measure 

 of the power developed by the steam-engine to which it is applied, and 

 registers the aggregate of that power during any required period of time. 

 The instrument consists of a small double-acting indicator-cylinder l^in. 

 in diameter, each end of which is connected by means of a pij^e with the 

 corresponding end of the steam-engine cylinder. These connexions are 

 made as short and direct as possible. The piston-rod of the indicator 

 carries a long toothed pinion, c, which revolves loosely on the rod, but is 

 held endwise between two screw-collars. This gears into a toothed wheel, 

 d, which is connected with and drives the indices. At the lower end of 

 the long pinion, and fixed to it, is a hght wheel, b, called the integrating 

 wheel, having a smooth rim with a rounded face. To the upper end of 

 the piston-rod is attached a spiral spring, which offers a resistance to 

 the free movement of the piston in its course from the middle to either 

 end of the indicator-cylinder; on a short horizontal shaft is mounted a 

 circular disk, e, whose face is constantly, but not forcibly, pressed against 

 the rim of the integrating wheel. This is effected by means of a light flat 

 spring bearing against the end of the shaft on which the disk-wheel is 

 mounted. A small cog-wheel,/, is keyed on the disk-shaft, and is con- 

 nected by a rack, or any other suitable means, to the cross-head or other 

 convenient reciprocating part of the steam-engine, or a small pulley, /, may 

 be keyed on the disk-shaft, round which is wound a cord, whose two ends 

 are attached to the cross-head or other convenient reciprocating part of the 

 steam-engine, being carried thence round loose pulleys above and below. 

 By either of these means the reciprocating motion of the steam-engine is 

 converted into a rotary motion of the disk acting in alternately opposite 

 directions. When there is no pressure on the piston of the steam-engine, 

 and accordingly none on the piston of the indicator, the integrating wheel 

 is so adjusted that the point of contact of its rim with the disk shall be at 

 the centre of the disk, that being the zero-point of the instrument. When 

 the pressure of the steam is admitted, so as to act on the piston of the in- 

 dicator, the integi-ating wheel traverses in consequence from, the centre 

 towards the circumference of the disk, the distance traversed being pro- 

 portionate to the pressure of the steam on the piston. tSuppose, now, the 

 cross-head of the steam-engine, and with it the disk of the instrum'ent, is 

 moving, such motion will be communicated by the disk to the integrating 

 wheel, and through it to the indices. The motion so given to the indices 

 during this stroke of the steam-engine is proportionate to the pressure of 

 the steam on the indicator-piston during that stroke. Let it now be sup- 

 posed that the stroke is finished and a return movement is commenced, 

 the disk will now rotate in the opposite direction ; and if the steam acting 

 upon the piston were pressing in the same direction as before, the inte- 



