22A1. General description. At the time this book was written, a new type of underwater log was in process of development. This log is known as the All s-Chalmers underwater log, and is manufactured by the Allis-Chalmers Manufacturing Company of Milwaukee, Wisconsin. The rodmeter element of the system consists of a small propeller, in the hub of which is placed an a.c. generator. The propeller head is secured to a bronze tube with provision for inserting and removing   through a 3-inch sea valve. Leads from the generator are brought up through the rodmeter tube to an electronic amplifier which in turn drives a small synchronous motor. A mechanism interprets the synchronous motor revolutions in terms of knots and nautical miles. Remote indicating stations are driven by the usual synchromotor system. Preliminary tests of these electronic logs give promise of extremely high accuracy even at low speeds.

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