[31] 



U. S. FISH COMMISSION STEAMER ALBATROSS. 



33 



the condenser, where there is from 2.°. to 26 inches of vacuum ; lying in 

 port, we let the boiler pressure fall to 25 pounds and exhaust the dy- 

 namo engine against pressure of the atmosphere ; and notwithstanding 

 this great difference of pressure between the two conditions, the governor 

 of the dynamo engine so regulates the quantity of steam to the cylinder 

 that the revolutions of the engine remain practically at 300, never vary- 

 ing more than 2 per cent. The engine and the dynamo are run by en- 

 listed men in the engineers' department. 



THE DYNAMO. 



The dynamo (Fig. 4) is of the size known as Z, and is wound for what 

 is called a B circuit, i. e., a circuit which will give 51 volts of electro- 

 motive force, and generate a current for 120 lamps, each requiring 

 0.745 amperes, offering a resistance of 69 ohms. The field magnets are 



Fig. 4. 



vertical, and the armature revolves on a horizontal axis, in the magnetic 

 field. The field magnets are arranged on what is called a " derivation " 

 or " shunt" from the commutator, placing it in the circuit as in the Sie- 

 mens system. In adapting and utilizing known principles and devices 

 and in patiently working out details, Mr. Edison has brought his system 

 of lighting to an admirable state of perfection ; wherever the eye rests 

 H. Mis. 67 3 



