Marine T/iermomeler. SO.** 



of the United States, without at least a sufficient warning of the 

 approach to danger, to allow of its being avoided, unless the ship 

 should be so cntlrelv disabled as to be totally unninnagcable. 



The stateiDents of Dr. Franklin and Colonel Williams apjjlied 

 only to the coasts of North America ; and Iience it came to be 

 generally supposed that the increased heat of the sea, when out 

 of soundings, was caused by the Gulf stream-current, which issu- 

 ing from the Gulf of IVJesico, sweeps to the northward along the 

 coasts of the United States: it has of late however been esta- 

 blished that the decreasing temperature of the water, as any ves- 

 sel approaclies the coasts of Spain, Portugal, and Barbary, is suf- 

 ficient to give warning to any attentive navigator of his approach 

 to these coasts; and it seems probable, from the experiments of 

 Mr. Davy, (brother to the celebrated Sir Humphry,) that the 

 thermometer will be found to point out, not only the proximity 

 of land, but also that of extensive banks, &;c. in all places. 



A person whose experience had shown him that in i|nitting 

 the American coasts, there was an increase of 12 deg. of Fahren- 

 heit's scale in the temperature of tlie sea in a few hours run from 

 the month of the Delaware, found also on approaching the coast 

 of Portugal, that the mercury in the tube of the thermometer 

 sunk from (J9 degrees, at which it stood in tlie open sea, to (J0\ 

 degrees, when his ship was about three or four miles from Cape 

 St. Vincent; and subsequently, that in heating through the 

 Straits of Gibraltar with a contrary wind, the mercury in the 

 thermometer rose and fell in proportion to tiie distance he 

 was from the' Spanish or African s^hores, ranging from 68 de- 

 grees, at which it stood in the middle of the Strait, to 61 degrees, 

 whicii was the lowest to which it sunk on the African side ; aiid on 

 the Spanish shore it never fell lower than 64 degrees ; which is 

 easily accounted for, as the ship was never so near that shore, it 

 being considered adviseable to keep at a distance from the shoals, 

 Sec. near Tariffa. 



The person already mentioned having discovered many objec- 

 tions to the mode of using the thermometer, recommended by 

 Colonel Willianis, and having had several thermometers broken, 

 applied to different mechanics in various [)laces to construct a 

 marine thermometer ease for him, which would protect the in- 

 strument and facilitate its use; but unsuccessfully until he some 

 time since applied to Messrs. Gardner and Jamieson, mathema- 

 tical instrument makers in Glasgow. Mr. Jamieson, of that firm, 

 invented and made a case, which not only prevents the thermo- 

 meter inclosed in it from being injured, but admits and retains 

 water from any depth which may be desired ; so that the results 

 obtained by the experiments made with it are exempted from 

 any chance of being influenced by the solar rays in sunimcr 

 M m 2 weather 



