Electric Currents of great Strength. 

 Wilde Machine (large size). 



171 



Resistance of 



circuit, in 



ohms. 



Current, in 



vebers per 



second. 



Speed of 



machine, per 



minute. 



Metre-grammes 



consumed per 



second. 



Equivalent of 

 current in metre- 

 grammes per 

 second. 



•594 



62-33 



548 



350-658 



235-480 



•733 



61-76 



508 



392-403 



285-293 



•857 



43-82 



532 



283-107 



167-907 



•907 



60-25 



500 



453-123 



335-966 



1039 



39-28 



520 



298-356 



163-682 



1-120 



4344 



548 



343-827 



215-660 



1-241 



50-43 



504 



542-685 



322 047 



1-453 



44-94 



520 



553-311 



309-658 



1-593 



47-51 



536 



633-765 



366-910 



2-305 



32-86 



528 



643-632 



253-968 



The measurements with the Wilde machine were made with 

 an electro-dynamometer similar to that described in Maxwell's 

 • Electricity and Magnetism/ It was constructed on the 

 Helmholtz-Graugain principle, and had a resistance of 58'9 

 ohms. A shunt of '1 ohm had to be employed ; and the in- 

 strument was also coupled in multiple arc to avoid the length- 

 ening of the bifilar suspension. 



Gramme Machine (large size). 



Resistance of 



circuit, in 



ohms. 



Current, in 



vebers per 



second. 



Number of 



revolutions of 



armature per 



minute. 



Metre-grammes 



consumed per 



second. 



Equivalent of 

 current in metre- 

 grammes per 

 second. 



•675 

 •760 



•781 



86-0 

 75-6 

 75-6 



432 

 462 

 452 



589-743 

 534-336 

 607-200 



509-418 

 442-211 

 455-377 



Siemens Machine (large size). 



•973 

 1-055 

 1-066 



79-8 

 688 

 66-0 



264 



294-5 



325 



831-105 

 743-820 

 839-454 



632-255 

 509-569 

 472-805 



I add a few data in regard to the dimensions of these ma- 

 chines, which are partly taken from the reports of the Secre- 

 tary of the Navy for 1877, and partly from the Station records, 

 which were generously placed at my disposal. 



The Gramme Machine. — This machine weighs about 2700 

 pounds, stands 30" high, is 40" long and 34" wide. It is 



driven by a pulley 15" 

 with very little friction. 



in diameter. The armature moves 

 The field-of-force coils are flat : and 



