1. Present-day mines may be divided into two general classifications – "controlled" and "independent". Controlled mines are mines which are controlled (fired) by an observer from a safe observation point. Independent mines are mines with self-contained firing mechanisms which function automatically. Independent mines may be subdivided as "contact" and "noncontact" or "influence" mines. In the former, the firing mechanism re-quires that an extending "horn" be moved or bent or that a wire "antenna" or some part of the mine be touched for the mine to fire. In the latter, the mere existence of metal, sound, or other disturbing influence in the vicinity of the mine may be all that is neces-sary to cause it to fire. The external appearance of a mine will not, in many cases, indi-cate the type firing mechanism used.

2. Independent mines may be divided into three types, depending on their final posi-tion in the water. These are:

(a) Drifting Mines. – Mines which float on or just under the surface of the water.

(b) Moored Mines. – Mines which are held under the surface of the water by a chain or wire attached to a heavy weight or "anchor" which rests on the bottom.

(c) Ground Mines. – Mines which are heavier than water and rest on the bottom.

3. All types of independent mines can be laid by aircraft, surface craft, and submari-nes. Controlled mines are laid by special surface layers.

4. The following points may be considered in identifying mines:

(a) Color. – Mines are normally painted black but may be other colors and are occa-sionally camouflaged. This paint frequently wears off, exposing red paint underneath. Where mine have been in the water for a long time, heavy marine growth may completely over the case and external fittings.

(b) Size and Shape. – Mines are usually spherical, spherical with a cylindrical section between the two halves, or cylindrical in shape, and vary in diameter from about 16 in-ches to 46 inches, and in length up to about 125 inches. There are, however, a number of mines of irregular shape which do not fall into any of the above classes.

(c) External Fittings. – Numerous fittings which are located in or extend from mine cases may be used for purposes of identification. These includes:

(1) Cover Plates. – Either one or both ends of mine cases are usually covered by co-ver plates bolted to the mine case. These plates normally vary from one to two feet in diameter.

(2) Horns. – Approximately two-thirds of all mines have horns extending from the mine case. These horns vary in lenght from ½ inch to over 1 foot, but are normally about 5 in-ches in lenght. The three most common types are a short copper spike, a long steel spike, and a thick lead horn. Where used, they vary in number from 3 to 11. Horns of mines which hase broken adrift are frequently bent or entirely broken off.

(3) Hydrostatic. – Many mines contain one or more devices located in holes in the mine case for operationg mechanisms within the mine. These devices usually do not ex-tend beyond the mine case.

(4) Mooring Wires and Antenna. – Most types of mines are connected to steel mooring wires or chains at one end. Several types have copper antenna wires (not over 100 feet in length) connected to the other end. These antennae are usually attached to steel floats (in most cases about 1 foot in diameter and 1½ to 2 feet in length), painted black and occasionally containing horns. Mine sweeping cables or normally wear may cause the float and any part of all of either mooring cable or antenna to be missing. Floats are fre-quently found by themselves, and as such are harmless.

5. In order to facilitate identification, the mines in this publication are arranged in the following order:

(a) Spherical mines. –

(1) Without horns. – Arranged in order of diameter with small mines first.

(2) With horns. – Arranged as above. Where two or more mines of same diamater are shown, the one with the fewest horns is shown first.

(b) Spherical with center section. –

(1) Without horns. – Arranged in order of diameter. Mines of same diameter are arran-ged in order of length.

(2) With horns. – Same as without horns.

(c) Mines with antennae and floats. –

(1) Spherical mines. – Arranged in order of diameter.

(2) Spherical mines with center section. – Same as (b) (1).

(d) Cylindrical and odd-shaped mines. – Same as (b) (1). Where a mine of a given type may be of more than one size, it is located by the smallest size.