14° Examination of St. Pierre's Hypothejis 



is elevated to a greater height than in open and deep oceans 

 that have fteen banks, becaufe the force of its motion is not 

 broken upon level fhores till the water has attained a greater 

 height. If a place communicates with two oceans, or by 

 two different openings with the fame ocean, one of which 

 affords an eafier and readier paffage than the other, two tides 

 may arrive at this place in different times, which, interfering 

 together, may produce a great variety of phenomena. 



At feveral places it is high water three hours before the 

 moon comes to the meridian ; but that tide which the moon 

 drives, as it were, before her, is only the tide oppofite to that 

 produced by her when nine hours paft the oppolite meridian. 



It would be tedious to enumerate all the particular folutions 

 eafily deduciblc from thefe doctrines : as, why lakes and feas, 

 fuch as the Cafpian and the Mediterranean, the Euxine and 

 the Baltic, have little or no fenfible tides; fince, having no 

 communication, or being connected by very narrow inlets 

 with the great ocean, they cannot receive or difcharge water 

 fufficient to alter their furface fenfiblv. In general, when 

 the time of high water at any place is mentioned, it is to be 

 underftood on the days of new and full moon : the times of 

 high water in any place fall at nearly the fame hours afler a 

 period of about fifteen days, or between one fpring tide and 

 another. 



This theory, however, is not without objections and diffi- 

 culties-; which has encouraged a Frenchman of fome emi- 

 nence, St. Pierre, to harm a new and Angular hvpothefis, 

 afcribing all the phrer. mena of the tides to the periodical 

 effufions of the polar ices. 1 (hall flrft mention the mod 

 material fa els and confider.it ions which appear to militate 

 agninft tie common theorv, as dated bv St. Pierre; and I 

 fha'l then endeavour to explain the theory he has fubltituted 

 (which it has cod me fome pains to collect, abftract, and 

 arrange), as nearly as pofhble in a literal tranflation of his 

 own language. 



ITisfaid that, if the moon acl:ed bv her attraction, her in- 

 fluence mud extend to the Mediterranean, the Baltic, the Caf» 

 9 pian, 



