62 6 THE POPULAR SCIENCE MONTHLY. 



electrical system will be untouched, but the engines will be re- 

 placed by motors operated by current from the falls station. 



As has been justified by the importance of the subject, there 

 have been some quite exhaustive experiments undertaken by vari- 

 ous scientists to determine the frequency of alternation at which 

 unsteadiness of the light from both incandescent and arc lamps is 

 observable or at least objectionable. Several independent experi- 

 menters have arrived at results sufficiently satisfactory to them- 

 selves, but which unfortunately can not be used as reliable data, 

 for the reason that they are highly discrepant with each other. 

 One reason for this is the evident one of the difference between 

 different makes of lamps, but the discrepancies are of a character 

 not altogether to be explained on that ground. With the ordi- 

 nary fifty-volt filament, however, it would seem that we may 

 place the working rate of alternation at about thirty or over; 

 with arc lamps, at about fifty or over. 



As above mentioned, the arc lighting will be done by making 

 use of the motor transformer (a motor operated by the power cur- 

 rent driving a dynamo generating, if we may call it so, the sec- 

 ondary current), but it is expected that by means of a special form 

 of incandescent lamp the Bernstein, which has, indeed, been on 

 the market for several years the twenty-five-period current will 

 be available for direct use for illumination by means of incandes- 

 cent lamps. It is evident that the thicker the filament the longer 

 will its incandescence take to die out (as well as to start up), and 

 a current of twenty-five pulsations, which may not be available 

 for the high-resistance (thin) filament, may be quite sufficiently 

 so for a low-resistance one, which the Bernstein lamp above men- 

 tioned is. 



The voltage at which the first installation of generators is "to 

 operate is somewhat over two thousand. Considering the perfec- 

 tion to which European practice has been carried in the construc- 

 tion of alternating-current machines for much higher electrical 

 pressures than the above, it seems strange that this voltage should 

 have been decided on in a situation where one would expect the 

 very highest degree of perfection to be attained. It is stated, 

 however, that it was largely on account of the comparatively 

 backward condition of that branch of electrical engineering con- 

 struction in America that the voltage had to be placed so low. 



In a case like the present one, where the power station will be 

 under the supervision of skilled engineers, and not merely of men 

 whose chief qualifications are those of sobriety and an ability to 

 stay awake at night, there appears no sufficient reason why the 

 generators should not be operated at five times the voltage named. 

 The fact of the armatures in these machines being fixed gives, 

 moreover, additional security against danger consequent on such 



