After the mines have been planted the following tests are made daily, or more frequently if need be, the results being recorded carefully on the form given at the end of the chapter. (Note: This applies also to such test mines as may be kept planted for purposes of observation and instruction.) =Caution.=—If A. C. power be supplied from the casemate motor-generator, there is no possibility of accidental firing of mines if the motor-generator is not running; and when it is running the chance is remote, since it would require the committing of three blunders. However, the following precautions must be enforced rigidly: (_a_) _Never start the motor-generator during the planting of mines nor when any friendly vessels are in the neighborhood of the mine field._ (_b_) _Before starting the motor-generator for testing it, see that all automatic switches are up, all firing switches open, and the A. C. operating switch (No. 8 of the power panel) open._ 1. =Test of the D. C. voltage.=—Plug in at the proper receptacle and read the voltmeter. 2. =Test of the A. C. voltage.=—_Caution._—_First see that all automatic switches are up, that the firing switches are open, and that the A. C. operating switch No. 8 is open._ Close switch No. 4 up; close starting switch of motor-generator, and when the latter has attained its full speed close switch No. 9 up; plug in at the proper receptacle, and read the voltmeter. When the source of power is the storage battery, the battery rheostat should be adjusted until the A. C. voltage is 500 or above; when the casemate generator is used, its field rheostat should be adjusted for the same purpose. 3. =Test of the mines.=—Leakage in mine circuits will be indicated automatically by an increased brightness of the green lamp on the signal block; an excessive leakage in any mine circuit may cause the automatic switch to trip. However, each mine should be tested separately, as follows: With the D. C. on the D. C. busses of the power panel, close switch 7 up, open the power switch on the mine block of the mine circuit to be tested, and put the M-AM “plug” on the upper point of the power switch. If the automatic switch falls, adjust the solenoid or hold the switch up while testing the circuit, otherwise the reading obtained will be that of the red lamp and bell circuit. These operations put the mil-ammeter and its protective lamp in series with the mine circuit.