July 26, 1889.] 



SCIENCE. 



53 



through the hollow shaft to the magnets. A rheostat (Fig. 4), 

 worked by hand or automatically, is placed in the shunt circuit 

 around the field-magnets'of the e.xciter; so that perfect regulation 

 is secured without re-adjustment of the brushes, or any^necessity 

 of handling the high-tension alternating current. 



is less than ten per cent, as is shown in the curve, Fig. 5, which 

 represents a diagram taken from one of the first machines. All 

 this is accomplished without compound winding or artificial regu- 

 lation of any kind, — a result which, it is claimed, has not been ap- 

 proached by any alternator with an iron core in its armature. All , 



■ BRUSH ALTERNATING SYSTEM. 



The Brush " coreless" alternator is built at present for an elec- 

 tro-motive force of 2,000 volts, although it would be easy to develop 

 a much greater difference of potential. It is confidently expected 

 that the necessity of long-distance transmission with a line of 



the regulation needed is applied at the e.xciter, as already described. 

 This results in a more even distribution of potential in the feeders 

 and at the converter terminals, and a more even pressure at the 

 terminals of the lamps beyond. 



G(.«,j,«ry 



FIG. 5. — BRUSH ALTERNATING SYSTEM. 



moderate cost will soon call for currents of higher tension, as 

 economy of power as well as economy of copper point in this di- 

 rection. 



The fall of the potential in the machine from no load to full load 



Though the high-tension current of the alternator is well adapted 

 for economical carriage to distant points, it is not of the kind most 

 desirable for introduction to the household, or for use in the lamp. 

 Having brought electric energy from the place where it is devel- 



