May 3, 1901.] 
but through the ammeter of large capacity. 
The anode of the electrolytic cell is there- 
fore always connected to the middle binding 
post and the kathode either to the post 1 or 
25, depending upon the strength of current 
it is intended to pass through the cell. The 
voltmeter, being connected as shown, meas- 
ures the potential differences at the termin- 
als of the cell, except for the addition of the 
small fall of potential through the am- 
meters. 
“The voltmeters on the side of the room 
SCIENCE 705 
against a backboard with a heavy felt gas- 
ket, making the joint. The wires come 
out through hard rubber tubes sealed at 
their outer ends by insulating tape. The 
rheostats are of the enameled type, chosen 
because of their being impervious to fumes. 
They have a total resistance of 172 ohms, 
divided into 51 steps in such a way that 
their resistances form a geometrical pro- 
gression. The first step, and the sum of all 
the steps, being chosen in accordance with 
data of the resistances of the baths deter- 
Fie. 7. Working Table. 
have scales ranging from 0 to 50, and di- 
vided to 1-2 volts. Those on the center 
table range from 0 to 120. 
- “The ammeters ranging from 0 to 1 am- 
pére are divided to 1-100 and those reading 
from 0 to 25 are divided to 1-5 ampéres. 
The three instruments are mounted side by 
side on an oak backboard extending the 
whole length of the room and are covered 
by an air-tight case with a glass front, as 
shown in Fig. 7. The cases have neither 
doors nor a back, but are simply screwed 
mined for the work done under the old 
system. 
“The wires, both those in the battery 
rooms and those in the laboratory proper, 
are covered with rubber, and those in the 
laboratory are further encased in oak 
molding, but this rather for appearance’s 
sake than for protection. The whole in- 
stallation, as well as the other fittings of 
the room have a very neat and finished 
appearance. 
The problems investigated by students in 
