353 



Electro Magnetism. 



be placed at e, and the wire connexions as "before directed. This 

 is at once a very beautiful and simple machine, but in order to re- 

 alize its full power, the two straight magnets should be charged 

 by separate batteries. It cannot be made very large with any 

 economy, and the proportions should be very different from those 

 seen in the figure ; the armatures should be much shorter than 

 the magnets. 



Figure 3, represents a revolving armature machine, invented 

 in the month of March, 1838. 



Fig. 3. 



The magnets b b b b are secured by brass screws to the braces 

 c c. The armatures a a are attached to two arms e e, which in 

 this case may be run upon a steel shaft. The electrotome is sim- 

 ilarly constructed and placed, and the connexions similar to those 

 of figures 1 and 2. This is the last of a series of experiments 

 made with reference to this subject, and after much attention, I 

 am inclined to give it the preference. Soon after this was in- 

 vented, a machine of larger size was built by the subscription of 

 several gentlemen in Boston. It contained eight magnets, four re- 

 volving armatures and the revolving system was one foot in diam- 

 eter. Not being able to be present during its construction, some 



