'T Derde deel van 't Licht der zee-vaert, inhoudende de beschryvinghe der zeecusten van de Middelandtsche...

of the day, not the 30th, but the 50th degree from the north towards the east, next to the copper edge original: "cantken" had stood, as at D, in such a case one should divide the arc A D, measuring 80 degrees, in two parts at

A circular compass rose diagram depicts a degree scale marked from 0 to 90 in four quadrants. Letters A, G, F, C, E, B, and D are placed along the upper half. A decorative fleur-de-lis points toward the markings for C and E. A sunburst star occupies the center.

E, such that A E and E D each measure 40 degrees. That being so, E is the true north point, and such a compass points with the fleur-de-lis from the north towards the west from E to C 10 degrees, which is very nearly one compass point A traditional nautical measurement of 11.25 degrees..

But if, in the aforementioned measurement after noon, the copper edge had stood 10 degrees westward of the fleur-de-lis as at F, one then divides the arc A F, measuring 20 degrees, into two at G, such that A G and G F each measure 10 degrees. That being so, G is the true north point, and the fleur-de-lis of such a compass points from the north towards the east from C to G 20 degrees, and so on with all other examples.

It is to be noted here that one may take measurements two, three, four, or more times before noon at different altitudes of the sun. For example: the first time when the sun is 10 degrees high, the second when it is 15, the third when it is 20 degrees high, and in the afternoon again at the same altitudes. From the comparison of so many different measurements, one finds how one corresponds with the other, and when one always obtains the same north point, one is more assured that one has measured well.

How to find the altitude of the sun from the shadow.

The common graedboogh degree-arc/quadrant is a very convenient instrument to take the altitude at sea, both for the sun and especially for the stars. But when the sun stands high, it is not as easy to use, because the heat and great brightness are very hindering to the eyes and hard to bear. To avoid this, one

can very conveniently find the sun's altitude from its shadow, as follows: Make a staff three or four feet long (depending on your preference), well planed straight, half an inch thick and two inches or more wide (so that it may always stay straight), as follows here A B. On the middle of the wide side (exactly halfway between the top and bottom