532 THE POPULAR SCIENCE MONTHLY 



The diminution of the mean range of tide in going westward from 

 Portugal indicates the existence of a no-tide point westward from the 

 Azores. Other no-tide points occur in European and American arms 

 of the Atlantic Ocean. The no-tide point between Holland and Eng- 

 land was first pointed out by Dr. Whewell and the one in the Adriatic 

 Sea by Dr. Sterneck. 



Indian-Ocean Tides 



The Indian Ocean contains two strips of water well suited to the 

 production of tides. The first extends from the northwestern coast of 

 Australia to the coast of Somali Land and Arabia, the second, from the 

 southern coast of Australia to the southern coast of Africa and Mada- 

 gascar — the southern edge of this strip resting upon the Antarctic Con- 

 tinent. The tides of the Bay of Bengal depend upon those generated 

 in the first strip, while the horizontal shading in the area between 

 Madagascar and Hindustan, taken in connection with the tidal hours, 

 indicates that an oscillation exists in this area which depends chiefly 

 upon the rise and fall of the tide at the southern end of Mozambique 

 Channel. 



The stationary character of the tide in the Bay of Bengal is shown 

 not only upon the small chart of the world, but also upon the chart of 

 cotidal lines which covers the Indian Ocean (Fig. 6). A vertical sec- 

 tion is shown by means of a diagram (Fig. 3). 



The distance southward from the southern coast of Australia to the 

 Antarctic Continent is less than a half wave-length of the lunar tide. 

 It is more nearly equal to a half wave-length of the solar tide. Con- 

 sequently the tides due to this oscillation are chiefly solar, and the tidal 

 hours are enclosed in parentheses for the sake of distinction. 



Fig. 6 shows that a great diversity of ranges of tide occurs in the 

 Indian Ocean. Between Ceylon and Sumatra the mean range of tide 

 is about one foot, while at the head of the Gulf of Martaban the range 

 is nearly 14 feet. In the mouths of the Ganges the mean range is 

 nearly 10 feet. At the southern extremity of Hindustan Peninsula 

 the mean range of tide is about 1.5 feet while at the head of the Gulf 

 of Cambay it is 23 feet. On the western coast of Madagascar the range 

 of tide is 8 or 10 feet, while at Tamatave, upon the eastern coast, it is 

 1.5 feet. At Freemantle, near the southwestern corner of Australia, 

 the range of the semidaily tide is 0.4 foot, while at Collier Bay and 

 King Sound on the northwestern coast the mean range of tide is about 

 24 feet. 



Between Madagascar and Hindustan is a no-tide point where the 

 rise and fall of the semidaily tide vanishes. 



Pacific-Ocean Tides 

 The tides in the Pacific Ocean are produced by two systems of oscil- 

 lations which are distinguished from each other by the two kinds of 



