at great depths, far from Land. 29T 



ed but to 2° below the temperature of the surface, whilst the same 

 thermometer, placed, as I have stated, in the place of the one bro- 

 ken by pressure, fell 11° : incontestible proof, in every I'espect, of 

 the superiority of our apparatus, and of the defectiveness of the 

 double valved cylinder. 



Third experiment of one thousand two hundred feet, by 5° north 

 latitude. 



The experiments above related have been made at inconsiderable 

 depths, and with a less perfect apparatus than the one of which I 

 have given a description ; it remains to describe two other observa- 

 tions of the same kind, more recent also, having been made during 

 our return voyage from India to Europe, with an instrument better 

 constructed, and at depths much greater. The 19th of February 

 1804, we found ourselves within the tropic, becalmed so that our 

 vessel remained motionless on the surface of the water ; to avail my- 

 self of such favorable circumstances, I desired the commanding offi- 

 cer to permit me to try some new experiments. I had previously 

 constructed my apparatus nearly in the manner I had conceived prop- 

 er. I sunk it to one thousand two hundred feet ; it remained there 

 one hour and fifty minutes, not including the time of drawing it up, 

 which was seventeen minutes. It was at twenty seven minutes after 

 five ; the atmosphere indicated +25° 1' of Reaumur ; the surface of 

 the water was at -{-24° 5'. My thermometer drawn from the depth of 

 one thousand two hundred feet, marked no more than +7° b', cold- 

 ness already very considerable, doubtless, and which had been much 

 greater, had it not been for the difficulties of which I have spoken in 

 the first experiment, the most part of which occurred in this. Nev- 

 ertheless, the results of this kind of experiment, always analagous to 

 the preceding ones become the more interesting, as they prove still 

 further the progressive lowering of the temperature in descending to 

 the bottom of the ocean. The following observation would have 

 dissipated all my doubts, had any remained. 



Fourth experiment of two thousand one hundred and forty four 

 feet depth, by 4° north latitude. 



The 22d of February, I to6k advantage of the continuance of the 

 calm to repeat my interesting trials ; two thousand one hundred and forty 

 four feet of cord, were sent to the bottom of the sea at fifteen minutes af- 

 ter eleven in the morning, we commenced drawing it up at thirty minutes 

 after noon ; it took forty five minutes through the ill will of the crew, 

 to whom observations of that kind afford little pleasure. The entire 



Vol. XVII.— No. 2. 11 



