APPENDIX. 89 



himfelf, however, feems to have been aware of the 

 neceffity of fubmitthig to the teft of experiment the ad- 

 vantages of a new meafurement derived from theory. In. 

 the preface to his Seaman s PraSiice he fays, " Becaufe I 

 " am perfuaded we have at this day as many excellent navi- 

 *' gators in this kingdom, and as great voy^ages performed, 

 " as from any other place in the world, I (hould be glad 

 " to hear of the experimental refolutionof this problem by 

 *' fome of them, though it were but running eight or ten 

 " degrees near the meridian ; for fo I doubt not but what 

 " I have here written thereof, would receive further con- 

 *' firmation and better entertainment than happily it will 

 " now, being fo much different from the common 

 " opinion." 



Had the errors in the diftance arifen onty from a 

 fault in marking the line, nothing would have been 

 more eafy than to have removed that difficulty, by 

 comparing carefully the different meafures with the ob- 

 fervations, and adhering to that which had been found to 

 correfpond beft with them. But the diftance meafured by 

 the log being rendered uncertain by many accidental 

 circumftances, it becomes difficult, or rather impoffible, to 

 find any length of line which will fhew invariably the 

 diftance run bv the fliip, or even to afcertain with precifion 

 that meafure which will at all times come neareft the 

 truth. Some of thefe circumftances are : 



P ^ I. The 



