242 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
the old one at the Washington Navy Yard, there are four separate 
model basins each designed for a particular line of work. 
The principal large deep-water basin is 963 feet long by 51 feet wide 
by 22 feet deep. Here models of large ships are towed or self- 
propelled. This is the largest basin of its kind in the world. 
Joining the large basin is a shorter shallow-water basin 303 feet long 
by 51 feet wide by 10 feet deep. The depth can be varied at will to rep- 
resent rivers, canals, and channels of limited depth and width. In 
this basin models of tugboats, barges, river craft, and other types of 
shallow-water vessels are tested. 
Forming a continuation of the west end of the shallow-water basin 
is a J-shaped turning basin, for testing the maneuvering and steering 
characteristics of models. In a special enclosure over this basin, 
accurate photographic observations of the models under test are made 
with a group of cameras about 40 feet overhead. 
To the north side of the large basin there is a high-speed basin 1,168 
feet long by 21 feet wide by 10 feet deep, for the testing of models of 
high-speed motor boats and seaplane hulls. Incidentally, the site is 
large enough to permit the extension of this basin to more than twice 
its present length to meet requirements of the future. 
In the basement of the main building is a small basin, 142 feet long 
by 10 feet wide by 514 feet deep, for the testing of special models and 
for unusual research problems. 
The towing carriages, which span the basins and operate on the 
precision-laid rails atop the basin walls, furnish the means of testing 
the models. The heart of a towing carriage is the dynamometer, 
which with its related recording instruments measures the forces 
arising from the motion of a model through the water. 
Two carriages are now in operation—carriage 1 over the deep-water 
basin, and a special quiet-running carriage with wood frame and pneu- 
matic-tire wheels over the high-speed basin. Under construction, and 
to be placed in service during 1944, are carriages for the shallow-water 
basin and the high-speed basin. The last carriage will have a top 
speed of 24 knots. 
The carriage which now operates on the deep-water basin is typical. 
The specifications it must fill are exacting: a testing speed range of 
from 0.1 to 18 knots, the selected speed to be constant during an 
8-second measuring run within 0.01 knot, a rigid-frame structure to 
span the 51-foot distance between the basin walls without permitting 
disturbing vibrations or deflections at the midspan where the measur- 
ing instruments are located, absolutely straight-line motion of the 
towing point where the model is attached to the carriage, a dynamome- 
ter to measure the model resistance during the measuring run to within 
