(1112) 
all this be done, we are not arrived at- what we call Yrintwg. But 
all' thole firevious Contrivances, muft be owned as Yarts of the 
Inveniion^ 
' ; And, in the Magnetkk Doilrhie likewife. And, to thofe pra- 
vious Difccveries, mnft be added, the Subfequem Improvements 
cf Magnetick Knowledge, fince the. fi.rft /^/^ of the MarinersCvm- 
-plls. But of this enough. 
I underftand, yj3U are engaged alfo in the bufinefs of the Tidet^ 
and'the Soir/idings m our Englijh Seas ( and to very good purpofe,) 
as well as the Magnetick Variations. Of which the one may pol- 
fibly be iubfervieur co the other. 
You may perhaps think fit, ( in order thereunto, ) to caft your 
Eye on my liypoihelis, IV JEfi'h Marps, Which, though a Ihort 
i flay, and pub|ifLed long fince, ( and but from a moderate know- 
ledge ,ot the Hiitcry ot Tiles contains (I think) much of Truth 
in it', and is capable of being Fpliflied, by thofe w^hoare better 
^acquainted v^ith thorfiiftory oif' Tifies, than I pretend to be. For 
I look upon thele Hypothefes as highly probable, which do natu- 
Tally follow from the general Laws of Motion duly confidered. 
And I cannot but think, that, as well .the Courfe and Variation of 
Tides as the Breezes and Trade-Winds m fcx^xdl pznsoi xh^ 
World-, and the Gz/vwrj- on ieveral Coafts^ with their Annual 
Viziffiiudes2ititxty<xiumts oixh^ year^ do all depend, in great 
meafure, en the Earths Motion^ with that of the Moon (it^ At- 
tendant,) and the'G?;;;^^'/^;^^ yH^/ii?;/ of Bothj with x\\€\h Co7mnon 
Center of Gravity, 
But 1 would not prejudge your fpeculations; who may have rea- 
fonto i Lifpeft alfo Ibme J;f^<f/?;y7f Motion. within the Body of the 
Earth, 61 which w^e are not well aware* 
SLR, 
Jours tofervi ycu^ 
John Wallist 
