154 TABLES OF OBSERVATIONS, ^'C, 



REMARKS. 



The figures written across the Tines ai'e the mean ot 

 the difference (when any difference occurs) between this 

 and Table V. It is very apparent, from these observations, 

 that although you most generally find the water become 

 progressively colder the farther you advance to the nortli- 

 ward, or as the season itself becomes colder, yet this does 

 not always happen ; so that it is utterly impossii^le to form, 

 with accuracy, such a Table as the ingenious Mr. Williams 

 has attempted. Yet he is certainly entitled to a great deal 

 of credit for the correctness of many of the deductions in 

 his work on Thermometrical Navigation, considering tiie 

 limited ex[)eriments he had anopportunity of making, in the 

 very few voyages performed by him. He ai)pears to have 

 been so sanguine, as almost to believe that this science 

 might be reduced to such perfection, as to enable the navi- 

 gator to ascertain thereby the ship's place at sea. Of the 

 fallacy of this hope, the continued experience and unremitted 

 application of more than ten years (to and fro in the same 

 track) have convinced me beyond a doubt. Nevertheless, 

 I shall ever esteem the thermometer as a very important 

 and useful instrument in navigation. Although it is not 

 entitled to that implicit confidence that should induce a 

 person to incur risks in running for the land or soundings in 

 dark nights, or thick foggy weather, yet it may often appiise 

 him of the vicinity of danger, wlien he does not expect 

 it. In navigafing the Atlantic, between the United States 

 and Europe, if bound to the westward, the necessity of shun- 

 ning the current of the Gulf Stream is obvious to evei y one, 

 as well as the propriety of making use of its assistance 

 when going in the opposite direction. The irregularity of 

 the courses it pursues, together with its undefined limits, all 

 of which are considerably changed by the prevailing winds, 



