Marine Thermometer Case. 297 



tact with the ship. Some gentlemen, whose opinions I respect- 

 ed, suggested that while towed by the ship, her way through the 

 water would naturally cause the thermometer to rise to the sur- 

 face, and that thus only the temperature of the surface water 

 could be obtained, and that they conceived this temperature lia- 

 ble to be influenced by the effects of the solar rays. To obviate 

 this objection, I saw the necessity of a case to inclose the ther- 

 mometer, which would admit the water freely as long as it was 

 permitted to descend, but would shut as soon as it was begun to 

 be hauled up. 



After I was satisfied how useful a thermometer case, adapted 

 properly for these purposes, must prove, I applied to various me- 

 chanics in different places to construct one for me ; but they ei- 

 ther did not sufKcientlv understand the matter, or considered the 

 safety of human lives and merchant ships and cargoes of too tri- 

 vial importance to induce them to exercise their abilities. Be 

 tliis as it may, I was always disappointed of my object, until I 

 became accidentally ac(|uainted with Mr. Jamieson, who readily 

 entered into my views, and made a case for my thermometer, 

 which completely answers my ideas, of which the model intended 

 to be sent to the Honourable the Society of Arts, &c, is, as you 

 know, a correct copy, i. e. allowing for the difference of sizes, 

 the original case being 1^\ inch in diameter within, which I con- 

 sider large enough to contain a column of water that will retain 

 its original temperature a sufficient space of time (after the case 

 is hauled up) to allow of the degrees indicated by the scale 

 l)eing read off by the observer, which is all that is necessary; 

 while, if the magnitude of the apparatus had been increased, it 

 must have become almost useless from its weight, when a vessel 

 had fresh way through the water, and by the time she came- to 

 run eight or nine knots, must have been totally unserviceable^ 

 The same objection applies to any addition of weight. 



The objection to .Jamieson's Marine Thermometer Case, which 

 has, I understand, been made, that the valves do not permit a 

 sufficient colunm of water to pass completely to fill the interior 

 of the case in a constant stream as it descends, appears to me of 

 little importance, as enough must pass through to regulate the 

 altitude of the mercury in the thermometer tube ; and before 

 there can possibly be tjme to haul up any part of the attached 

 line, the mere pressure of the water must infaUibly fill the tjjer- 

 mometer case. 



Furdy's Memoir shows incontcstably, that no vessel on board 

 of which there is a thermometer, can possibly run ashore on the 

 coasts of the United States of America to the northward of the 

 Strait of Florida, without her commander (unless he is guilty of 

 the most culpable negligence) having at least warning in sufficient 

 Vol.r.7. No. 21 i\. Jpril \m\. P p time 



