_Austrian Testing Table._--The following is a description of the Austrian testing table, and their mode of making electrical tests with it, in connection with their system of self-acting electrical submarine mines. [Illustration: METHODS OF TESTING.--ARMSTRONG,--AUSTRIAN. PLATE XXVIII] Its design is shown at Fig. 100; _c z_ represents the battery with one pole to earth at _e_, and the other in connection with an intensity coil _a_, through which the current passes to the contact plate _b_. When it is desired to put the system of mines in connection with the table, in a state of preparation to be fired by the contact of a vessel, a plug is inserted between the contact plates _b_ and _f_, and the current passes through the galvanometer _g_, and electrically charges the conducting wires connecting the mines with the battery, through the several binding screws on the contact plates, numbering 1, 2, 3, &c. The fact that the charge has been fired is also at once indicated on the galvanometer _g_. _Test to discover an Exploded Charge._--It then becomes necessary to ascertain which particular mine of the system has been exploded; for this purpose a separate circuit in connection with a single cell _d_ is employed. This cell is in connection through a galvanometer _g'_ (a more sensitive instrument than the galvanometer _g_) with the pivot of the key _h_, and rheotome _R_, which latter is connected, as shown by the dotted lines, with each individual mine of the system attached to the contact plates numbered 1, 2, 3, &c. The handle of the rheotome is moved round, to each number in succession and directly it is placed in contact with that corresponding to the exploding mine, the electrical circuit is completed through the exposed end of the fractured wire, and this is indicated by the galvanometer _g'_. During the testing process the firing battery _c z_ must be disconnected; this is done by raising one of the bridges _i i_ with which each group of ten mines is provided.