VOL. XXXIII.] I'HILOSOPHICAL TRANSACTIONS. 3Q 



An Attempt to account for the rising and falling of the Water of some Ponds 

 near the Sea, or ebbing and flowing Rivers; where the Water is loivest in 

 the Pond, at the Time of high Water in the Sea or River; and the Water 

 is highest in the Pond, at the Time of low Water in the Sea or River. 

 As also for the Increase or Decrease of the Water of such Pools and 

 Brooks as are Jughest in the dry Seasons, and loivest in the rainy Seasons: 

 With an Experiment to illustrate the Solution of the Phcenomena. By the 

 Rev. J. T. Desaguliers, LL. D. and R.S.S. N° 384, p. 132. 



Hero, and other hydraulic writers, have described a cup, called a tantalus, 

 from its effect, which will hold any liquor very well, when it is not filled above 

 a certain height marked in the cup ; but if it be filled higher, not only the 

 liquor above the mark will run out, but the whole liquor that is in the cup. 

 This is performed by a syphon in the cup, which is sometimes concealed to 

 make the effect the more surprising. 



The cup, AB, fig. 1, pi. 1, has a visible syphon ced in it; the cup fig. 2 

 has the same, concealed by the figure of a man, to represent Tantalus in the 

 Fable ; and the cup of fig. 3 has its syphon more concealed, as it is carried up 

 into the handle. Any of these cups will hold water very well, provided they 

 are not filled up above the line fg ; for then, not only the liquor that is above 

 FG will run out, but all the liquor in the cup as low as d, the orifice of the 

 short leg of the syphon. 



Exper. \, fig. 4. In the vessel abed is placed an open wooden box abcd, 

 filled with water as high as the line lm. Another box or plug efgh made 

 tight, and containing weights to sink it, is made to let down into the water 

 between the partition ik and the end ab of the former box; but when it is not 

 to press the water up to lo, as it does when let down, it is drawn out of the 

 water by the weight m, which pulls it up by the bar ik, fastened to a leaver 

 moving round the centre 1. 



When by means of the plug, the water in the space abki is pushed up to 

 lo, by passing under k; it runs out through the spout pa, whose passage is 

 gauged by a little sluice pp, and falls into the vessel rs, made of an oblong 

 figure like a fish-pond, and having a syphon at s, so as to make it a tan- 

 talus, or in the nature of the cups abovementioned. 



Let the weight m draw up the plug efgh; then the water, having filled 

 RS, will run down below the orifice p to m. The tantalus rs, beginning to run 

 out as soon as full, will, for the reasons above given, continue to run till it is 



