Form of Ergometer. 



89 



the planimeter; or, if the paper is of great homogeneity, the 

 area may be cut out out and estimated by weight (this method is 

 Morin's). The author finds that far the best results are obtained 

 by the use of tinfoil or thin lead instead of paper, as paper is sub- 

 ject to damp and rapid variation of weight. In order that the 

 instrument may be of considerable range, springs of different 

 strengths can be easily interchanged. Since the weight of 

 the indicating rod and bar is slight, the indications are dead- 

 beat. A speed-indicator (this is Young's form of instrument), 

 R, showing the number of revolutions at any instant, is 

 attached to the hollow shaft, and is so placed that its reading 

 and that of the tension-indicator can be seen at a glance. This 

 is found sufficient for most purposes; but when continuous 

 work is being done, such as charging a Faure battery, then 

 the diagram-drum is attached. 



For a continuous record, the following form of integrating 

 apparatus has been also employed : — 



Hydraulic Integrating Apparatus. 

 In using the ergometer, it is not always necessary to attach 

 the recording drum, unless some special curve be sought for, 

 such as that which is produced when the instrument is mea- 



suring the work done in 

 charging an accumulator. 

 The following apparatus 

 has been devised by the 

 author to take the place 

 of a disk integrator. 



A very small double- 

 acting pump, D, oscilla- 

 ting about the point H, 

 and having a long rod, 

 E Gr, not shown at full 

 length in fig. 3, is actuated 

 by a link AB (rocking 

 about the point B), to 

 which reciprocal motion 

 is given by the connect- 

 ing-rod, 0. This rod 

 receives its motion from 

 the revolution of the shaft; 

 the position of the end of 

 the pump-rod, E, and 

 hence the length of the 

 stroke, is controlled by 

 the rod E F, which is con- 



Fig-. 3. 





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Li 



Uh 



(/ 



Phil Mag. S. 5. Vol. 15. No. 92. Feb. 1883. 



H 



