Pasteur’s New Method of Attenuation. 6718
Convenient Vaults. 6719
in the Spanish Court at the late Fisheries Exhibition. 6722
Duck Shooting at Montauk. 6723
* * * * *
Apparatus for use in laboratories and cabinets of physics were quite numerous at the Munich Exhibition of Electricity, and very naturally a large number was to be seen there that presented little difference with present models. Several of them, however, merit citation. Among the galvanometers, we remarked an apparatus that was exhibited by Prof. Zenger, of Prague. The construction of this reminded us of that of other galvanometers, but it was interesting in that its inventor had combined in it a series of arrangements that permitted of varying its sensitiveness within very wide limits. This apparatus, which Prof. Zenger calls a “Universal Rheometer” (Fig. 1), consists of a bobbin whose interior is formed of a piece of copper, whose edges do not meet, and which is connected by strips of copper with two terminals. This internal shell is capable of serving for currents of quantity, and, when the two terminals are united by a wire, it may serve as a deadener. Above this copper shell there are two identical coils of wire which may, according to circumstances, be coupled in tension or in series, or be employed differentially. Reading is performed either by the aid of a needle moving over a dial, or by means of a mirror, which is not shown in the figure. Finally, there is a lateral scale, R, which carries a magnetized bar, A, that may be slid toward the galvanometer. This magnet is capable of rendering the needle less sensitive or of making it astatic. In order to facilitate this operation, the magnet carries at its extremity a tube which contains a bar of soft iron that may be moved slightly so as to vary the length of the magnet. Prof. Zenger calls this arrangement a magnetic vernier. It will be seen that, upon combining all the elements of the apparatus, we can obtain very different combinations; and, according to the inventor, his rheometer is a substitute for a dozen galvanometers of various degrees of sensitiveness, and permits of measuring currents of from 20 amperes down to 1/50000000 an ampere. The apparatus may even be employed for measuring magnetic forces, as it constitutes a very sensitive magnetometer.
[Illustration: Fig. 1.—Zenger’s universal rheometer.]