Isaacs—Faughn—Schick-Sargent: Deep-Sea Moorings 279 
abrasion. All others showed evidence of having been fouled by ships, eut free by 
fishermen, or, in several instances, bitten off by sharks. A broken shark tooth was 
recovered embedded in the end of one parted pennant. 
TYPES OF MOORINGS 
Many types of moorings are possible, and the type used should depend upon the 
specific requirements for the work at hand. A mooring may be slack or taut and 
may have either surface or submerged floats or both, and the depth of the sub- 
merged float may be specified. The mooring cable itself, as well as the floats, may 
or may not be instrumented. The degree of horizontal and vertical stability of the 
entire system or of particular elements may be of concern. The required longevity 
of the installation may be hours or months. Servicing at intervals may or may not 
be required, and servicing may be accomplished in situ or by retrieving and re- 
placing the instrumented station and part of the upper pennant. 
In this discussion we will consider only single-wire moorings, but two, three, or 
more mooring wires are possible, and may be necessary if the requirements for 
rigidity or minimum excursion are of paramount importance. 
As explained in Bascom’s paper (1953) the taut mooring was originally con- 
sidered because it provided a relatively fixed point of reference to which water 
motions could be related. It should be pointed out and perhaps emphasized, how- 
ever, that often the requirements for rigidity and minimum excursion will be the 
most difficult to meet and, where they are severe, may well multiply the cost and 
the complexity of the mooring many times. For these reasons alone it is advisable 
that the requirements for rigidity be carefully scrutinized each time with a view 
to reducing them to the minimum consistent with the results desired. An extreme 
example may be cited, in which one design of a station envisions the use of twelve 
separate anchors and is estimated to cost 27 million dollars! 
An additional and important point is worth considering. In many instances it 
may be better to design instruments to filter out or otherwise compensate for some 
motion in the moored system than to impose unduly severe and perhaps costly 
requirements on the mooring. 
The mooring must be so designed as (1) to provide the elasticity required 
to permit harmless dissipation of impulsive forces resulting from motions of the 
float in waves, and (2) to provide sufficient strength to resist the drag on the 
floats and the mooring component due to currents and wind. The anchor must be 
heavy enough to withstand the vertical components of the maximum pull, and 
it must engage enough shearing resistance of the bottom deposits to withstand the 
horizontal component of the maximum cable pull. 
The slack-wire mooring is essentially a mooring of large scope. Basically its 
restraint to excursion under increased forces depends upon increased tension in 
the mooring line. Hence the major portion of the buoyancy of such a system must 
be on the surface, where these increases in tension may be balanced by increased 
displacement of the surface float. Unless the design of a slack mooring is very eare- 
fully undertaken, the lower portions of the line may become fouled on the bottom 
and may part (or at least greatly reduce the scope). A very ingenious slack moor- 
ing, invented by A. Vine of Woods Hole Oceanographic Institution, has been in 
