The mariners magazine, or, Sturmy's mathematical and practical arts containing the description and use of the scale of scales, it being a mathematical ruler, that resolves most mathematical conclusions, and likewise the making and use of the crostaff, quadrant, and the quadrat, nocturnals, and other most useful instruments for all artists and navigators : the art of navigation, resolved geometrically, instrumentally, and by calculation, and by that late excellent invention of logarithms, in the three principal kinds of sailing : with new tables of the longitude and latitude of the most eminent places ... : together with a discourse of the practick part of navigation ..., a new way of surveying land ..., the art of gauging all sorts of vessels ..., the art of dialling by a gnomical scale ... : whereunto is annexed, an abridgment of the penalties and forfeitures, by acts of parliaments appointed, relating to the customs and navigation : also a compendium of fortification, both geometrically and instrumentally / by Capt. Samuel Sturmy.

The Ʋse of the Table of Proportion, for the more ready find∣ing out of any Logarithme, from 10000 to 100000.

WHen you have any Logarithme or Number above 10000, you may find it out as before, by the Differences which are in the last Column of the Tables: But for your more easie and ready performing it, this Table is of great use; wherein you have all those Differences ready divided, and cast into 10 parts: So that between each of the 10000 Logarithmes in the Table, you may easily know the ten Intermediate Logarithmes, by the Proportional Part of the Difference for any of them.

Thus in the Table the Logarithme of 2000 is	3.301029
The next Logarithme, being the Logarithme of 2001, is	3.301247

Alter the Characteristicks of these Logarithmes,

So have you the Logarithme of 20000,	4.301029
And the Logarithme of 20010,	4.301247

The Difference between these two Numbers is 218; which for the ten Intermediate Logarithmes must be divided into 10 Equal Parts, which is ready done in the Table of Proportion, after this manner.

D	1	2	3	4	5	6	7	8	9
318	31	63	95	127	159	190	222	254	286

So that the Logarithme of 20000 being	4.301029
The Logarithme of 20001, by adding 31, is	4.301060
The Logarithme of 20002, by adding 63, is	4.301092
And so for the rest, to 20010.

Or, on the other side, Let your Logarithme given be 4.301251, and you desire to know what Number answers to it; the next Number less in the Tables is 301029, which is the Logarithme of 20000: but this is 222 more, and the Common Diffe∣rence in the Table is about 218; turn therefore to this Difference in the Table of Proportion, and there you shall see that 222 makes your Number 7 more: So that 4.301251 is the Logarithme of 20007.

And thus you save the Labour of multiplying and dividing the Differences in the Table of Logarithmes, they being here ready done to your hand.