186 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



other words, the character of the tide would depend upon the latitude 

 of the place. 



Newton had proved that it was the attracting forces of the sun 

 and moon, with differing effects upon the solid earth and the waters of 

 the oceans, which gave rise to the tides. Further development of this 

 theory and of the problem of the tide has been the work of many 

 eminent mathematicians, including Bernoulli, Euler, Laplace, Airy, 

 Lord Kelvin, Poincare, and others in Europe ; and in the United States, 

 Ferrel and Harris. 



TIDES AT VARIOUS PLACES 



Knowledge of tidal causes and conditions becomes important when 

 they affect navigation, commerce, and the lives of people who live close 

 to the sea. Most of the great ports of the world are situated on tidal 

 waters, and the state of the tide is an important feature. The schedules 

 of ocean liners and of large modern steamers can usually be arranged 

 to take advantage of the more favorable conditions of the tide and 

 tidal current for entering ports and docking in congested harbors. 



It is frequently necessary for a steamer to traverse many miles of 

 tidal waterways. For example, we may cite the Inland Passage to 

 Alaska where there is a considerable fluctuation in the rise and fall 

 of the tide. Except for the entrances into the main inlets and sounds, 

 numerous islands restrict the inside route. The navigator must know 

 the state of the tide at critical places along his course. Shoal water 

 in a strait between two main inlets, which would be hazardous at low 

 tide, could be navigated without danger at a higher stage. 



As a member of the United States Coast and Geodetic Survey field 

 party on board the ship Mac Arthur, which made the original hydro- 

 graphic surveys of Cook Inlet, Alaska, I recall our difficulties in 

 erecting tide staffs to measure the great range of the tides in the 

 vicinity of the present city of Anchorage. At that time there were 

 no piers or other structures to which the staffs could be secured. Mud 

 flats extended offshore for several miles from the high-water mark. A 

 series of staffs were erected across these flats, and an observer, stationed 

 in a small boat, recorded the tide as it rose or fell on successive staffs. 

 Near this location, our record measurement was a 35-foot difference 

 in height between high and low water. 



The need for information on tidal conditions in our coastal waters 

 became apparent toward the close of the last century when systematic 

 hydrographic surveys were inaugurated in pioneer regions and in 

 some rapidly growing seaports. This need brought about the develop- 

 ment of the automatic tide gage and of improved mathematical equip- 

 ment for analyzing tidal observations. With such gages installed at 

 strategic tidal locations, we have been able to accumulate much infor- 



