the iron rim, and c c are the zigzag coils of copper ribbon. The field
magnets are also wound in a similar manner.

It will be seen from our description that Drs. Hopkinson and Muirhead
have scarcely had sufficient credit given them for this interesting
machine, which so closely approximates to the Ferranti. One of their
alternating dynamos has been built, and was shown at the Aquarium
Exhibition. It works well, and is capable of supporting 300 Swan lights,
while in size and appearance it resembles the Ferranti machine in a
very striking manner. Drs. Muirhead and Hopkinson have also designed
a magneto-electric alternating current machine; but as it closely
resembles the machines described, with the exception that permanent
magnets are employed as field magnets, we need not dwell upon it
further.--_Engineering_.

* * * * *




AN IMPROVED MANGANESE BATTERY.

By GEORGE LEUCHS.


The Leclanche battery is distinguished for its simplicity, its small
internal resistance (0.7 to 1.0 Siemens unit), and that all chemical
action ceases when the current is broken, that it is not sensitive to
external influence, and by the self-renewal of the negative electrodes.
But on the opposite side the action is not very great (= 1.20 or 1.48