OF DENISON UNIVERSITY. 33 



hours a week, from a dynamo we would be able to draw about 

 i^ horse power of energy (as light, heat or power) from the stor- 

 age cells for the same number of hours. In this way the in- 

 convenience of using primary batteries about the laboratory can 

 be largely avoided. 



A simple plan for a dynamo and storage battery outfit would 

 be to have a constant-potential dynamo of about 50 volts and a 

 storage battery of the same voltage with motors, lamps and gen- 

 eral apparatus all adapted to this pressure, to run the dynamo 

 at full capacity as much time as may be necessary to charge the 

 battery (doing other work at the same time,) and to use the stor- 

 age battery alone for the general work of the laboratory at other 

 times. For a large laboratory building, a combination of the two 

 plans would be useful. Use a dynamo of higher potential, say 

 1 10 volts, for the general work of the laboratory, at least all 

 heavier work such as supplying power for mechanical work- 

 shops etc ; let the dynamo at the same time charge a 55 volt 

 battery and run 5 5 volt apparatus placed in series with it in the 

 special rooms most likely to be used at odd times when it is 

 not conv^enient to have the dynamo running. The lamps and 

 apparatus can then be used at any time when the machinery is 

 idle by means of the storage battery. This is the plan now be- 

 ing introduced in the new Barney Laboratory of this college. 

 There remains the case of the laboratory equipped with alternat- 

 ing current. Tight either from incandescent or arc lamps is di- 

 rectly provided for. All heating effects can be produced as 

 well by SL«h currents — a class of uses which will doubtless be- 

 come very much extended in the near future. For charging 

 storage cells and for use with most demonstration apparatus al- 

 ternating currents are not suited, but alternating motors might 

 run direct-current generators to supply the current for such 

 purposes. 



All that has been said of alternating currents will apply to 

 the three-phase and multiphase currents now being introduced 

 for conveying power and light to a distance, but such currents 



