STORAGE BATTERIES. 181 
Each cell contains sixteen plates, whose united weight is forty-eight pounds, 
and with the lead-lined box and liquid, the entire weight of the cell when in use, 
is seventy-nine and a half, or say eighty pounds. 
One of these cells full charged will yield, as I have found by careful experi- 
ment, a current of 32.5 amperes at the beginning, and 31.2 amperes at the close 
of a continuous discharge for nine hours. 
This amounts to 286.5 ampere hours of current, and if even short interrup- 
tions or periods of repose occur in use of the current a yet larger total amount can 
be obtained. 
An Edison incandescent lamp of high resistance, giving a light of sixteen 
candles, requires a current of . 73 of an ampere to supply it. Such a current, 
therefore, as these batteries yield for nine hours at a time, will suffice for forty- 
four such lamps. 
To secure sufficient electro-motive force or propelling power to overcome 
the resistance of these lamps would, however, require about fifty of such cells, so 
that a battery of fifty of these cells connected in series, would operate forty-four 
lamps for nine hours^ or for even a longer time in the aggregate, if the use were 
interrupted, as it would be in practice. If fewer lamps were used with the same 
battery, they would be operated for a proportionately longer time. 
Thus eleven lamps would be supplied by a fifty cell battery for thirty-six 
hours of continuous action ; or as fights are commonly used in private houses, on 
the average for five hours each night, such a battery once charged, would operate 
eleven lamps for a week. 
To express the relation between weight of battery and power of maintaining 
a light, we might, therefore, say that for each lamp operated for|nine hours, one 
and a seventh cells of battery would be required, or a weight of about ninety 
pounds of battery. This would be for each hour of burning each lamp, ten 
pounds of battery. 
This makes a very simple rule for calculating the weight of battery required 
for any number of lamps for any time. Thus, suppose we wish a battery to 
operate twenty-five lamps for five hours each night, the battery being recharged 
during the day. We have 25x5x10=1,250 pounds as the weight of battery- 
required. 
Comparing the efficiency of this storage battery with that of other similar 
arrangements, such as the Faure battery, measured and reported upon by M. 
Tresca, of the "Conservatoire des Arts et Metiers," itjshows a marked superior- 
ity. Thus in M. Tresca's experiments a cell weighing ninety-five pounds yielded 
a current representing 793,791 foot-pounds of energy where your battery yields, 
as I have stated above, 1,826,168 foot-pounds and only^weighs eighty pounds. 
Your battery, therefore, yields more than twice^the energy and weighs almost 
one-fifth less. 
Even the experiments made some time afterwardsjby Professors Ayrton and 
Perry, on other Faure accumulators, though the conditions were rendered as 
favorable as possible by distributing the discharge^over|three periods of six hours 
