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.

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Title
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.
Author
Sturmy, Samuel, 1633-1669.
Publication
London :: Printed by E. Cotes for G. Hurlock, W. Fisher, E. Thomas, and D. Page ...,
1669.
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"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." In the digital collection Early English Books Online 2. https://name.umdl.umich.edu/A61915.0001.001. University of Michigan Library Digital Collections. Accessed June 15, 2024.

Pages

The Arithmetical way.

Thus. AB × AC. × AD / 144 = to the Contents in feet. 38 128/144

Or thus. AB × ACAD / 1728 = reduced into inches 168 in 14 foot 38 1536/1728 feet, as before found.

Yet it is common with the Carpenters to add the broad and narrow side together,* 1.1 and to take the ha•••• thereof; the true Square that way is very erroneous, especially when the difference between the side is much.

[illustration] geometrical diagram

In the former Example one side is 25, the other 16, the Sum 41, the half 20 50/100 inches; that is, half an inch too much, as was proved by the former Rules; that is just 20 for the Mean or true Square: so that by taking ½ the 2 sides 20 ½, it makes the piece of Timber 40 foot 4/10, when indeed it is but 38 9/10 feet, which is 1 foot and half too much.

Now if a Piece of Timber that is tapering, the Common Rule is to take the Mean betwixt both ends; and so to Work as in the last Form, but it is not absolute true.

Notes

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