1677'] 
An account of the courfe of the Tides at Tonqueen in 
a Letter from Mr. Francis Davenport July i 5. 
1678. with the Theory of them^ at the Barr of 
Tonqueen, hy the learned Edmund Halley Feline 
Roy al Society. 
WHen the reported irregularity, ot the Ehhing and 
Flowing of the Sea came firft under my confide- 
ration at a diftance, I was content to fancy that 
I had gueffed aright in afcribing the occafionof it princi- 
pally to t\\t Indraughts and outlets of this bay, which as I 
Imagined might give (the different times of the year in 
relped: of the Monfoons^ and the currents accordingly 
(hitting with feveral other conceited coadjutant circum- 
ftances,) the moft confiderable lhare in the unafual courfe 
of the T^'^^f^J-^and that confequently i t would fcarfebe pof- 
lible to difcover any conllancy in them, if their regi- 
ment depended fo much upon accidents and uncertain- 
ty's. 
But during my continuance ^tBatJhal have obierv- 
ed fuch an order and conftancy iri the courfe of the tides ^ 
that notwithflanding I muft needs confefs it dnreieiit 
from all that ever I oMerv'd in any other Port^yet not only 
from the coincidents of fmular alterations on peculiar 
dayesof fome particularMo^??/^ .r, in different wi?;y(?i?;7j" in 
refped: of their increaie and decreafe, as well asirom 
their keeping equatpace with the fifing and fctt- 
ing in this Hori^on^ in refped: of the duration of their in- 
flux and r^/i/^i, but alfo from that which feems to render 
them moft irregular, vi^, the conflant falliDg back of the 
flood nearefl 13 hours on every lecond day of the waters 
age and increafe, fo that at the end of daycs thereis 
an inverfion of their motion in refped ot their beginmg . 
to plow and Ebb. 
It is evident that they are regularly influenced though 
not reconcileable with a dependance on the////^^rmo- 
rion 
