Page:Philosophical Transactions - Volume 001.djvu/225

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Numb. 13.



Munday, June 4. 1666.

The Contents.

Certain Problems touching some Points of Navigation.Of a new Contrivance of Wheel-Barometer, much easier to be prepar'd, than others.An account of Four Suns which lately appear'd in France; and of two, unusuallv posited, Rainbows, seen in the same Kingdom.A Relation of an Accident, by Thunder and Lightning, in Oxford.An Experiment, to examine, what Figure or Celerity of Motion begetteth or increaseth Light and Flame.Some Considerations touching a Letter in the Journal des Scavans of May 24. 1666.

Certain Problems Touching some Points of Navigation.

THese Problems are presented by the Learned and Industrious Nicolaus Mercator, for the advancing of that Excellent and Beneficial Science, Navigation, as follows:

The line of Artificial Tangents, or the Logarithmical Tangent-line, beginning at 45 deg. and taking every half degree for a whole one, is found to agree pretty near with the Meridian-line of the Sea-Charte; they both growing, as it were, after the same Proportion. But the Table of Meridional degrees being calculated only to every Sexagesimal minute of a degree, shews some small difference from the said Logarithmical Tangent-line. Hence it may be doubted, whether that difference do not arise from that little errour, which is committed by calculating the Table of Meridional degrees only to every minute.

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