Powers of ' Electro-Magnetism, Steam, and Horses. 453 



diameter, and f^ths of an inch thick, cut longitudinally to 

 prevent the circulation of electrical currents in the iron, and 

 furnished with a coil of 210 feet of covered copper wire T \jth 

 of an inch thick. A steel magnet consisting of a considerable 

 number of bars was fitted up in order to excite those ends of 

 the straight electro-magnets which were distant from the large 

 steel magnets. The coils were arranged for quantity. 



Experiment 5. — Current when the engine was kept still, 

 2081; current when the armature was revolving 11 4 times 

 per minute, 1300; consumption of zinc, 291 grains per hour; 

 power developed, 10030 lbs. raised a foot per hour. Hence 

 the theoretical duty will be 



158 (2081 - 1300) _ 



2081 ~~ ' ' 



and the actual duty, 



10030 .„ „ 



^9T = S4 ' 5 ' 



Experiment 6. — Current before starting, 2035; current 

 when revolving 192 times per minute, 1000; consumption of 

 zinc, 223 grains per hour; power developed, 12,672 lbs. 

 raised a foot per hour. In this case the theoretical duty will 

 be 



158 (2035 - 1000) _ on , Q . 



2035~~ - 8 ° 3 ' 



the actual performance will be 



-223"- 568 * 



The mean of the six experiments gives a theoretical duty of 

 78*5, and an actual duty of GS'G. But, making allowance for 

 the hot solution employed in the first two experiments, we 

 may state that the actual was in general about f ths of the theo- 

 retical duty. 



Upon the whole we feel ourselves justified in fixing the 

 maximum available duty of an electro- magnetic engine worked 

 by a Daniell's battery at 80 lbs. raised a foot high for each 

 grain of zinc consumed*, or, in other words, at about half the 

 theoretical maximum of duty. 



Before we leave this part of the subject, we may state that 

 the above experiments fully bear out the idea expressed by 



* Dr. Botto states that 45 lbs. of zinc consumed in a Grove's battery are 

 sufficient to work a one-horse power electro-magnetic engine for 24 hours. 

 The intensity of Daniell's battery being fths of that of Grove, it follows 

 that 75 lbs. of zinc would have been consumed had Dr. Botto employed a 

 Daniell's battery, — a result not widely different from our own. 



