Oceanography, the science of the oceans, tries to bring to light all the changes that take place in the physical and chemical properties of water at various depths. Dozens of research ships of different nations designed for complicated ocean research are criss-crossing the oceans. They are fully equipped for a long navigation and for a wide range of scientific work, they can sail safely for many thousands of miles without putting into port. Scientists are engaged in day-to-day weather watches and oceanographic observations made aboard ship. Their task is to measure the winds, the temperature of the seas, water velocities in the deep layers of the ocean and to conduct other important studies.
Different measuring instruments, wave recorders and tide gauges are at work. A special instrument is used to record rapidly the temperature of the water at all depths. These temperature readings are most important in the study of the oceans, for the seas are reservoirs not only of water, but of heat that stabilizes the world's climates. Another modern instrument enables us to determine the motion of the ocean water by measuring the electric potentials induced in it because of its movements through the earth's magnetic field.
The invention of the supersonic echo sounder has revealed that the floor of the ocean is covered with great mountain chains and deep trenches. This device is based upon the principle of sending down sound impulses to be reflected and recorded on a special receiver. Echo sounding instruments now have developed to such a degree that it is possible to obtain a continuous accurate profile of the sea bottom under the surveying vessel's course. Moreover, a special meter is used to indicate depths by measuring the time required for a sound impulse to travel to the sea bottom and for the echo to return.
By means of special devices we are able to take specimens of soil and rocks from the deep ocean bottom which was inaccessible before and thus learn the origin of the ocean bed. To form one inch of soil on the bottom of the ocean takes thousand years, so it is easy to imagine what a remote geological past we can study in this way.
Special cameras may be used to photograph the ocean bed, the photographs showing any rocks and living organisms that happen to be in its field of vision. Such pictures can be taken at depths of more than 3 kilometers.
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