aetna ELAN rs Enon NY ne. nel ln amma 
— 
TO STUDENTS CERTAIN ELECTRICAL OPERATIONS. 159 
natural to suppose that the plate is entirely aie ent - electric 
fluid? To the same effect is the easy 28 in Ganot’s lees: 
itself over the ‘ore and if : co nd lection be: brought near it a 
8 ark passes.”” I do not see how a beginner’ could ve 
well avoid the peri that i cover is thus entirely deprived 
of its electric fluid. 
Then as to the action of the electrical machine, Tyndall says— 
“When the glass plate is turned by a handle it passes between 
po 
negative electricity and repelling its positiv ctor 
i th pots from which negative electricity streams 
ou igus the excited glass. Th ape ime conductor is 
with positive fluid. The ans esas gives up 
nothi he the conductors ; in fact, it only abstracts from them 
their ir negative fluid.” In other books usually i in t 
students the statements are equally liable to misconstruction. 
Tn explaining electrical excitation by the two-fluid theory, I 
consider it — to show that the total quantity of electric 
fluid belonging to a body is never aa but its quality may be 
changed by the Seales Sida of a portion of the one fluid for an 
equal portion of the other. The cena or unelectrified condition 
may be assumed as consisting of the two fluids combined in equal 
proportions. Whenever this Pee seman is om any way dis- 
turbed—that seine he the electric fi a ae 
one kind, or is more th se remersng ear ear praire perch accused 
proper to the body never ersten Ee we have e. excita- 
tion or charge. Take, for example, a glass tube anda sill ruber 
each with its own pro ak yoann ure of neutral electric a when 
- they are rubbed toget pound fluid on 
on 
gets 
or partially Coarmpeees the whole’ or part of the 
