[Illustration: FIG. 15.--HARLACHER'S APPARATUS FOR STUDYING DEEP
CURRENTS IN RIVERS.]

We have now exhausted the subject of the apparatus of precision that
were comprised in the Munich Exhibition. In general, it may be said
that this class of instruments was very well represented there as
regards numbers, and, on another hand, the manufacturers are to be
congratulated for the care bestowed on their construction.--_La
Lumiere Electrique_.

[Illustration: FIG. 16.--HARLACHER'S APPARATUS FOR STUDYING DEEP
CURRENTS IN RIVERS.]

[Illustration: FIG. 17.--VON BEETZ'S CHRONOGRAPH.]

* * * * *


COPPER VOLTAMETER.


Dr. Hammerl, of the Vienna Academy of Sciences, has made some
experiments upon the disturbing influences on the correct indications
of a copper voltameter. He investigated the effects of the intensity
of the current, the distance apart of the plates, and their
preparation before weighing. The main conclusion which he arrives at
is this: That in order that the deposit should be proportional to the
intensity of the current, the latter ought not to exceed seven ampères
per square decimeter of area of the cathode.