(215) Nm», i 3- 
PHILOSOPHICAL 
TRANSACTIONS. 
Munday 3 June 4. 1 665, 
The Contents. 
Certain Problems touching fom Points of Navigation, Of a new 
Contrivance of Wheel- Barometer , much eafier to be prepar*d 3 than 
others. An account of Four Sans which lafely appeared in France; 
and of two 0 unufualiypQf ted t K3.\nbows,feen in the fame Kingdom. 
A Relation of an Accidently Thunder and Lightnings in Oxford. 
An Experiment , to examines what Figure or Celerity of Alo-tion 
hegetteth or insreafetb Light and Flame. Some Confederations 
touching a Letter in the journal des S cava ns of May 24, 1 666 , 
Certain Problems 
Touching form Points of Navigation. 
6 
Hefe Problems are prefented by the Learned and 
Induftrious Nicolaus MercatorjCor the advancing 
'if&g BBr* of that Excellent and Beneficial Science 3 N^^<s- 
The line of Artificial Tangents , or the Logarithm 
mical Tangent-line , be ginning at 45. deg. and taking every half 
degree for a whole one , is found to agree pretty neer with the 
Meridian-line of the Sea- Char ted they both growing, as it were, 
after the fame Proportion. But the Table ot Meridional degrees 
being calculated onely to every Sexagesimal minute of a degree, 
fhews fame final! difference from the Laid Logarithmic al Tan- 
gent-line. Hence it may be doubted , whether that difference 
doe not arife from that little errour, which is committed by cal- 
culating the Table of Meridional degrees onely to every minute*. 
Gg Mr* 
