148 PHILOSOPHICAL TRANSACTIONS. [aNNO l6g7. 



S. W. moon makes high-water, and the same is reported to be on the west 

 side of America. But it would be endless to recount all the particular solutions, 

 which are easy corollaries of this hypothesis ; as, why the lakes, such as the 

 Caspian Sea, and Mediterranean Seas, the Black Sea, the Straits, and Baltic, 

 have no sensible tides : for lakes, having no communication with the ocean, 

 can neither increase nor diminish their water, by which to rise and fall ; and 

 seas that communicate by such narrow inlets, and are of so immense an extent, 

 cannot in a few hours' time receive or empty water enough to raise or sink their 

 surface any thing sensibly. 



Lastly, to demonstrate the excellency of this doctrine, the example of the 

 tides in the port of Tonquin in China, which are so extraordinary, and differing 

 from all others we have yet heard of, may suffice. In this port, there is but 

 one flood and ebb in 24 hours; and twice in each month, viz. when the moon 

 is near the equinoctial there is no tide at all, but the water is stagnant ; but 

 with the moon's decimation there begins a tide, which is greatest when she is 

 in the tropical signs : only with this difference, that when the moon is to the 

 northward of the equinoctial, it flows when she is above the earth, and ebbs 

 when she is under, so as to make high-water at the moon's setting, and low- 

 water at the moon's rising : but on the contrary, the moon being to the south- 

 ward, makes high-water at rising, and low-water at setting; it ebbing all the 

 time the is above the horizon. As may be seen more at large in N° 162, of the 

 Philos. Trans. 



The cause of this odd appearance is proposed by Mr. Newton to be from 

 the concurrence of two tides ; the one propagated in 6 hours out of the great 

 South Sea along the coast of China ; the other out of the Indian Sea, from be- 

 tween the islands in 12 hours, along the coast of Malacca and Cambodia. The 

 one of these tides being produced in north-latitude, is, as has been said, 

 gieater when the moon, being to the north of the equator, is above the earth, 

 and less when she is under the earth. The other, which is propagated froni 

 the Indian Sea, being raised in south-latitude, is greater when the moon, de- 

 clining to the south, is above the earth, and less when she is imder the earth ; 

 so that of these tides, alternately greater and less, there come always suc- 

 cessively two of the greater and two of the less together, every day ; and the 

 high-water falls always between the times of the arrival of the two greater 

 floods ; and the low-water between the arrival of the two less floods. And the 

 moon coming to the equinoctial, and the alternate floods becoming equal, the 

 tide ceases, and the water stagnates : but when she has passed to the other side 

 of the equator, those floods, which in the former order were the least, now 

 becoming the greatest, that which before was the time of high-water, now be- 



