72 ixTRODtJCTro.Nr. 



requisite means for astronomical determinatiotrs 

 of place, that is, good sextants and chronometers^ 

 and skill to use them. The method which has 

 been formerly proposed to lay a boat, as it were, at 

 anchor, to a lead let down to a great depth, is 

 partly troublesome, not always applicable, and, 

 above all, uncertain, because only a very small 

 part of the effect of the current is thereby dis^ 

 covered, and even that not completely^ because it 

 is highly improbable that the motion of the sea 

 should take place only at a small depth. 



Count Rumford has, by theoretical arguments^ 

 rendered it probable that there are in the ocean 

 two main currents, one of which flows on the sur- 

 face from the equator to tlie poles, and the other 

 at the bottom from the poles to the equator. It 

 is worth the attention of the mariner to notice all 

 such phenomena as may serve to confirm or to con- 

 fute this conjecture, as well as to lay hold of those 

 facts that are connnected with the motions of the 

 sea, which every where lays the ice to the eastern 

 coasts. 



A method which has not yet been sufficiently 

 practised, to get acquainted with the great ocean 

 currents, is the throwing out of well corked bottles, 

 containing a note marking the date, and the ship's 

 latitude and longitude ; some of those dispatches 

 have made voyages so remarkable for rapidity and 

 for distance, that frequent repetitions of the ex- 

 periment are higlily desirable, and the mariner 



