Calorific Power of various Liquids. 429 



be circular; the cork should be an inch long, and the 

 bottle weigh 76.07 grammes without its cork. 



The cylindrical vase which contains the water is two 

 inches diameter, and four inches nine lines high, and it 

 weighs 74.65 grammes. 



The exterior vessel, in which the latter is suspended 

 by the cork ring, is five inches three lines high, and 

 three inches diameter, so that the sides and bottom are 

 everywhere separated by an interval of six lines; this in- 

 terval is filled with eider-down, as already mentioned. 



To prevent the water from touching the eider-down, 

 the cork ring is covered with a thin coating of mastic. 



In order to ascertain the temperature of the bottle, 

 and of the liquid which it contains, without being 

 obliged to plunge a thermometer into the bottle, which 

 would in this case be inconvenient, I employed a very 

 simple method. 



I placed a large bucket filled with water in a room 

 with a northern aspect. I allowed it to assume the 

 temperature of the room, taking care to shut the door 

 and windows day and night. I placed the small bottle 

 on a stand in this bucket, keeping the upper part of the 

 cork only out of the water. As the bottle is small and 

 has a large surface, it speedily acquires the temperature 

 of the bucket of water ; but, in order to be well con- 

 vinced that the bottle and the liquid which it contains 

 have acquired the temperature in question, I leave the 

 bottle a considerable time in the bucket, frequently half 

 an hour and sometimes more. 



In giving a detailed account of an experiment made 

 with this apparatus, I shall have an opportunity of giv- 

 ing clear and precise ideas of the different parts of my 

 apparatus, and of the particular objects which they are 

 intended to attain. 



