Shore Testing Station.-At the same time, a location for a testing station was found at Yorktown, Va., where the necessary deep water, available dock, and desirable secrecy were combined. A layout for a railroad, derricks, shop and other equipment on the dock were designed, and arrangements made with the Bureau of Yards and Docks to have the work on this equipment started

at once.

Purpose and Operation of Testing.-As the Winchester was being fitted out, her commanding officer, Lieutenant W. I. Frost, U. S. N. R. F., was given instructions in the operation of testing, and the complement of the ship was increased to carry on this work.

The purpose and method of testing will now be briefly described.

As previously stated, paravanes contain a mechanism for controlling the depth at which they travel. British experience had proved that even the most careful shop inspection of a paravane would not determine whether it would run smoothly at its proper depth or not. It was, therefore, necessary to test each paravane by towing it in the water under practically the same conditions under which the paravane would be used. The only difference in these conditions is the point from which paravanes are towed. In service, they are towed from the forefoot of the vessel, while in testing they are towed from the after deck.

A starboard and port paravane are tested at the same time. Paravanes are manufactured port and starboard, the principal difference being the position of the rudder and also the weight and float on the ends of the plane. The weight is always on the lower end and the float on the upper end of the plane when running. The object of the weight is to cause the plane on the paravane to lie in a nearly vertical position when at rest on the surface so that when the ship starts to pull, it will at once start out from the side of the ship. The rudder, by having up helm, will cause the paravane to submerge at the same time.

Fig. 5 shows the two paravane towing ropes leading from the stern of the testing ship Winchester. By measuring the angle at which each towing rope cuts the surface of the water, the depth and variation in depth of the paravane are determined.

The freeboard of the vessel at the stern forms the base of a right angle triangle, one side of which is the surface of the water. The towing rope is the hypothenuse. Fathom and half fathom marks are attached to the towing rope so that the distance on each rope from the chocks to the water may be easily determined by the eye of the observer. The base and hypothenuse being known, the angle required is figured. A certain correction is applied to

the starboard and a different correction is applied to the port rope for the reason that, due to the twisting action of the water on the wire rope, the starboard rope hogs and the port rope sags, as will be noticed in the photograph.

Each paravane is tested at the maximum speed for which it is to be used in service. Type " M " paravanes are tested at 16 knots; type "B" at 22 knots; type "C" at 25 to 28 knots.

The operation of testing is carried out as follows:

The paravanes are inspected carefully at the testing station on the dock and set to run at 20 feet depth. They are then put overboard and towed out to the testing ship by launches, a port and starboard paravane being delivered at the same time. The testing ship proceeds immediately on the testing course, increasing her speed gradually to the maximum necessary for the type under test, and holding that speed for a full three minutes. If a paravane oscillates more than 5 feet above or below the depth for which it is set, it is not passed by the inspector. At the end of the test the ship is stopped and the paravanes are hauled in and made fast on either side of the ship, close inboard. The ship then returns to the station, lets go the two tested paravanes and picks up a fresh pair from the launches. An inspection slip, showing the record of each tested paravane is delivered to the launch with the paravane so that the record of each paravane is returned with it to the testing station. Under ordinary conditions the testing ship tests a pair of paravanes every 20 minutes.

When a paravane has passed test and is ready for service, a history sheet for that paravane is started. On this sheet is recorded the serial number of the PV. and the adjustments made by the testing station to make it run properly. The history sheet follows the PV. wherever it is shipped. Each transfer and each. adjustment of rudder is recorded on this sheet.

Each paravane when shipped from the testing station is set to run at a depth of 20 feet. Instructions are given for each ship to reset her paravanes to run at a depth of 5 feet below her own draft. Vessels drawing over 30 feet, however, are instructed to set their paravanes to run at a depth of 35 feet.

Confidential Handbook.-As it was considered necessary that each vessel being fitted with paravanes should have a book containing full information as to theory, construction, maintenance and operation of paravanes, the Bureau proceeded to compile and

published a confidential handbook called the "PV. Handbook" for the use of naval officers. A copy was forwarded to the commanding officer of each battleship, cruiser and transport, the Bureau requiring a signed receipt for each. At the same time, another handbook called the "Otter Gear Handbook " was compiled, containing information necessary for merchant ship captains, and copies of this book were furnished to the Emergency Fleet Corporation for distribution to their vessels.

Selection and Equipment of Instruction Ship.-As it was necessary to have an instruction ship to train merchant ship captains, as well as naval officers, the Bureau suggested to the Fleet Corporation that they furnish a vessel for this duty, the navy to operate her and direct the course of instruction. The Corporation accepted this suggestion, and the steamer Berkshire, of the Merchants and Miners Line, was offered. As this vessel was not fit for overseas transportation, and yet was of sufficient size to make her a suitable. ship to operate paravanes, she was accepted. The Emergency Fleet Corporation commandeered the ship and started at once to install, under the supervision of the Bureau, the necessary gear to make her a paravane instruction ship.

At the same time the Navy Department commandeered a small gasoline oyster boat called the Bivalve, and fitted her out as a mine layer to work in connection with the instruction ship.

As shown in Fig. 1, it is necessary that PVs. be towed from the forefoot of the vessel, this being the apex of the wedge formed. by the towing ropes. To meet the conditions required by different types of ships, three different devices for towing paravanes were developed. All three of these devices were fitted to the Berkshire, so that the captain of any ship could receive instructions on the particular device he would have to operate.

These will now be described:

In Fig. 6 is shown the bow of the Berkshire with the three devices attached. All have the same purpose, namely, to carry the forward ends of the towing ropes down to the forefoot of the vessel as close to the base line as practicable. As the towing ropes have a limited life, each device is constructed so that it can be hoisted or lowered for replacing ropes while the ship is under way.

The first device, used quite generally on battleships, cruisers and transports, is called the clump and chain. This consists of

two chains leading from the deck through chocks on the bow down through holes in the so-called clump or skeg, returning to chocks on the other side of the bow. The towing ropes are attached to a special swivel connection on the chains, and then hauled down close to the hole in the skeg. The towing point is

hauled down on either side by hauling up the chain on the other side of the bow.

The second device is called the boom device, developed for use on merchant ships of speeds under 14 knots. As is seen in the figure, the boom when in its down position reaches practically to the base line. It is prevented from swinging further down than