IOWA ACADEMY OP SCIENCES. 
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a firm coherent mass; and second, that the oxide of copper 
produced electrolytically slowly dissolves. I find, how- 
ever, from experience, that these defects do not preclude 
the use of this class of storage cell for student laboratory 
work. In fact, I think they are much better than small 
lead cells. When the cell is not too highly charged, the 
zinc adheres quite firmly to an amalgamated brass elec- 
trode. Furthermore, when the sub-oxide of copper dis- 
solves, it is probably at once reduced by the dense mesh of 
elastic steel netting which lines the can and which thus 
prevents it from affecting the deposited zinc. The result 
of the breaking down of the oxide, however, is to render 
the voltage unstable. A cell inactive for a period of time 
polarizes easily and its discharge efficiency is considerably 
impaired. Despite this, I find that a small-sized cell of 
this kind will give a better account of itself in continuous 
laboratory service than any lead cell of twice its weight. 
