Can) 
Which kerns to obfervc this or fome fuch like Proportion which is fuppoled 
{lill to hold in ail Tides, be the Duration whac it will ^ the Increafc Pali 
continuing proportionably till the very midie 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 here fuppofed to be in the different degrees cC 
the Velocity of the Current of the Water alter fpaces of Times, as in 
its Rifing and Failing : And fo it is markt in ihcThird Column. But becaufe 
the true Velocity of the Current of the Water, raifcd above the Levell 
r^lo of afoot, is unknown, it is by way of Suppofition fee at Ten feet in 
one Minute of anHour,which being once ftated, the rell diftant from each 
other by the fpace of lo.Minutes of an Hour,are fet down according to tlx 
fame Proportion of Signs before fuggefted. It being fuppofed, that of the 
Velocity of the CurrtKt of the l ide, after it hath flowed minuts of 
an hour, be fuch, a$ a Log of Wood placed in the Water will move lo foot 
in the fpace of one minute of time, at the mddle of the Fide it will in the 
hke fpace of Time move 1 14 f- ^ti*, and fo proportionably at other times : 
Which, howfoever thcfe Proportions fh^ill be found by Experiments tof^^ll 
out, may be not unworthy of the pains and charges requifite to acquire the 
knowledge of it. For, befidcs the fatisf^dion it may afford upon other ac- 
counts, it may pofsibly be of no fmall ufe tothofe, who need an exad rec- 
koning of their Ships running, when the Velocity of the Current of the 
Tide may be neceffary to be known left through the defcd of the know- 
ledge of that, cfpecially when it is reckoned lefs than indeed it is, the Ship 
be thrpwain the night upon Shores, flocks or Sands, when they reckon them- 
feives to be far from them* 
The Numbers in the 4, 5, ^, 7, and 8 . Columns are fet down at random, 
only for Examples fake ; there being no difficulty in the apprehenfion of it, 
and imitating of it in fetting down the true Hights and Variations of the 
Thermometer^ Barofcope^Scc, The Use whereof is fo vulgarly known, ths£ 
there needs no further Direftion 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 GreJhamColUdge^ from whom he will receive full 
fatisfaftion about thefe things. 
But the labour employed in the Obfervations of the Heat, Cold, &c. 
required to be taicen notice of in order to the Ends propofcd in the former 
Tract,zti4i others that may be of no lefs delight than advantage^ will be 
much retrenched, when Dr. Chriftopher tVren puts in pradice,what he fome 
years ago propofcd to the Royal Society concerning an Engine with a Clock^-^ 
work^ which may perform thefe Obfervations in the laft enumerate Columns ^ 
without being toucht or lookt after but once or twice a day* 
The Tabksthcmfelvcs follow, 
T a l€66. Seft^ 
