The semicircle on a sector in two books. Containing the description of a general and portable instrument; whereby most problems (reducible to instrumental practice) in astronomy, trigonometry, arithmetick, geometry, geography, topography, navigation, dyalling, &c. are speedily and exactly resolved. By J. T.

PROBL. 3.

A speedy way to measure any quantity of Board.

The two former Problems are sufficient to measure small parcels of Board. When you have occasion to measure greater quantities, as 100 foot, or more, lay all the boards of one length together, and when the length of the boards exceeds 12 foot, use this propor∣tion.

As the length in feet and inches is to 12, so is 100 to the breadth in inches for an 100 foot. Ex. gr. At 30 foot in length 40 inches in breadth, make an 100 foot of board (reckoning five score to the hundred.) This

found with a rule or line, measure 40 inches at both ends in breadth, and you have 100 foot. When one end is broader than another, you may take the breadth of the over-plus of 100 foot at both ends, and taking half that sum for the true breadth of the over-plus by Probl. 2. finde the content thereof.

When your boards are under 12 foot in length, say,

As the length in feet and inches is to 12, so is 50 unto the breadth in inches for 50 foot of board, and then you need only double that breadth to measure 100 foot as before. In like manner you may measure two, three, four, five, a hundred, &c. foot of board speedily, as your occasion requires.