TROWBRIDGE. — HIGH ELECTROMOTIVE FORCE, 189 
use wood separators; these wood separators are somewhat broader than the lead plates 
and a centimeter longer. They reach to the hottorn of the glass containing tube, while 
the lead plates are lifted from the bottom of these tubes about a centimeter. The 
active material, therefore, which might fall to the bottom of the cells cannot sh it- 
circuit the cells. The separators consist of strips of wood 1 mm. thick. When they are 
saturated with the dilute acid, they do not oppose any appreciable r istanoe. The use 
of w r ood separators in storage cells was discovered by Mr. E. P. Usher in a remarkabii 
installation at Milford, Mass., which served as the source of electric power for trolley 
cars on the route between Milford and llopedale. Mr. D r w, i the first to show 
I that they did not oppose any appreciable resistance, and that they prevented tin 
trouble of buckling. With the employment of these wood separators the experimental 
battery which I describe in this memoir can be short-circuit cd without danger to the 
battery 
Figure 1, Plate XXV, shows one tray of the battery with wood 
ing to the bottom of the tubes. Lead 
f the cells to the 
switches on the back of 
old the cells. Tl 
from each row of cells to the switches connecting the rows of cells, a distance of 
lead wires should 
proximately, 50 cm. It was found necessary that these 
cally from the cells through a distance of 4 or 5 cm., in order that the acid 
up the wire should drain b 
dripping 
up 
m the wooden supports of the cells. These lead win- do not touch the wood* 
any point, and do not rest upon any insulators save two porcelain insulators wh 
are directly above the end cells on each shelf. It was found, as I have said, that if 
they were led through glass tubes inserted in wood, the glai in time became covered 
with an acid solution which was communicated to the wood in which the lass tubes 
were inserted, and the wood thus became conducting. The liquid in the cell dilute 
sulphuric acid, is covered with a thin layer of paraffine oil to prevent evaporation. 
The acid solution is renewed about once in three months to replace the loss due to 
ition. The lead plates in the course of two or three years become friable, 
having become almost entirely converted into active material, and therefore need to 
be replaced. This replacement, of course, depends upon the use of the battery. 
Thicker plates would lengthen the life of the cells, but would also lead to greater 
poi 
weight. 
An open construction of each compartment of the battery is desirable, in order that 
the condition of the cells can be easily seen by passing an incandescent lamp behind 
the rows of cells. This open construction is shown in Figure 3, Plate XX V. It 
