C 3 1 i ) 
which feerm to obferve this or fome fuch like Proportion •, which is fuppofed 
llill to hold in all Tides, be the Duration what it will ^ the Increafe frill 
continuing proportionably till the very midle of the Hight and Duration,and 
Decreafing afterwards in the fame manner; Which whether it be fo indeed 
or not, is tha t, which is defired to be known. 
There is the like Proportion herefuppofed to be in the different degrees of 
the Velocity of the Current of the Water after I?*?#*/ fpaces of Times, as in 
its Riling and Falling : And fo it is markt in the Third Column. But becaufe 
the true Velocity of the Current of the Water, railed above the Level! 
&i| 0 f a foot, is unknown, it is by way of Suppolition fet at Ten feet in 
one Minute of an Hour,which being once ftated, the reft diftant from each 
other by the fpace of lo.Minutes of an Hour, are fet down according to the 
fame Proportion of Signs before fuggefted. It being fuppofed, that of the 
Velocity of the Current of the Tide, after it hath flowed 20 minuts of 
anhour,be fuch, as a Log of Wood placed in the Water will move 10 foot 
in the fpace of one minute of time, at the middle of the Fide it will in tbe 
like fpace of Time move 1 14 f. ,***-, an( j fo proportionably at other times ; 
Which, howfoever thefe Proportions (hall be found by Experiments to ft 11 
out, may be not unworthy of the pains and charges requifite to acquire the 
knowledge of it. For, befidcs the fatisfaftion it may afford upon other ac- 
counts, it may pofsibly beofnofmallufe to thofe, who need an exad rec- 
koning of their Ships running, when the Velocity of the Current of the 
Tide may be neceffaryto be known j left through the defed ol the know- 
ledge of that, efpecially when it is reckoned lefs than indeed it is, the Ship 
be thrown in the night upon Shores,Rocks or Sands, when they reckon them- 
felves to be far from thenv 
The Numbers in the 4, 5, 6,7, and 8. Columns are fet down at random, 
only for Examples fake • there being no difficulty in the apprehenlion of it, 
and imitating of it in fetting down the true Flights and Variations of the 
Thermometer , Barofccpe^&iCo The Use whereof is fo vulgarly known, thsC 
there needs no further Dire&ion concerning them. But if any perfon who 
would make thefe Experiments, do not know the fabrick or ufe of any of 
--the Inftruments requifite for fome of thefe Obfervations, nor where to have 
them, he may addrefs himfelf to Mr» Shortgrave^ one of the Operators of the 
Royal Society , lodged in Grefsam Co Hedge , from whom he will receive full 
fatisfa&ion about thefe things. 
But the labour employed in the Obfervations of the Heat, Cqld, dec. 
required to be taken notice of in order to the Ends propofed in the for mer 
Tract, and others that may be of no lefs delight than advantage, will be 
much retrenched, when Dr. Chrifiopher wren puts in practice, what he fome 
years ago propofed to the Royal Society concerning an Engine with a Clock* 
V0K k. y which may perform thefe Obfervations in the laft enumerate Columns s 
without being toucht or lookt after but once or twice a day. 
The Tabks themfelves follow? 
T a 1 666. Sept * 
