Electro-Magnetic Apparatus and Experiments. 253 



Having asserted thus much of the magneto-electric machine, 

 it will be necessary to allude briefly to the objections to machines 

 for electrolytic uses, where the galvanic battery is the primum 

 mobile. 



First. — The opposing currents produced by making and break- 

 ing the battery circuit cannot be separated, or rather cannot be 

 united to form one current. In the magneto-electric machine, 

 the alternating currents are made to flow in the same direction 

 by the pole changer, or more properly in this connection, the uni- 

 trep. As it is desirable that every distinct and useful apparatus 

 should have an appropriate name, I have selected the term Uni- 

 trep, as short, and descriptive of the use of this part of the mag- 

 neto-electric machine. This important addition to the machine 

 appears to be beyond simplification, consisting merely of two 

 nearly half cylindrical pieces of metal, rivetted or secured in any 

 manner to the circumference of a small disc of wood or ivory, 

 and insulated from each other. Its use, as the name Unitrep 

 implies, is to convert, or turn contrary currents into one com- 

 mon channel. 



Secondly. — In the galvanic magneto-electrical machines, elec- 

 tro-chemical eifects can be obtained (to any considerable degree) 

 only by distinct impulses, occurring at each ruptnre of the cir- 

 cuit. These impulses or secondary currents closely resemble a 

 common electrical discharge, and are of too short duration to 

 allow the particles of the substances to be decomposed to assume 

 definite polar arrangement. Nor can the circuit be broken rap- 

 idly to any advantage ; for in the first place, the full magnetiza- 

 tion of the iron requires appreciable time, and, secondly, the 

 flowing of the secondary through a completed circuit, weakens 

 itself by re-magnetizing the bar : (this wil' be spoken of in fu- 

 ture.) In the pure magneto-electric machine, water is decompo- 

 sed far more rapidly by the continuous current than by breaking 

 the circuit, by the primitive than the secondary current. The 

 secondary furnishes the most powerful shocks, but the primitive 

 possesses the greatest decomposing power. 



Compound Electro- Magnet and Electrotome for Rhodes., 

 Sparks, Sj'c. 



In the late numbers of Sturgeon's Annals, I notice that Mr. 

 Eachoflher has introduced the bundle of wires as superior to the 



