HEAT. 



11 



plying the heat of a spirit lamp to a 

 liquid contained in a bulb, such as de- 

 scribed in the last experiment, differing 

 only in having its tube divided into a 

 number of equal 

 parts. The num- 

 ber of divisions past 

 which the liquid 

 rises in the first five 

 minutes having been 

 observed, the same 

 heat applied during 

 five minutes more 

 will occasion a 

 greater expansion ; 

 and, consequently, 

 the liquid rising in 

 the tube will pass by 

 a greater number of 

 divisions in the se- 

 cond than it did in 

 the first five minutes. 

 Every successive 

 portion of heat ap- 

 plied produces an in- 

 creased effect, until 

 the water arrives at 

 the boiling point. In 

 explaining this fact, it is said that the 

 particles of the fluid have existing 

 amons; them a certain force of cohesive 

 attraction, which resists the expansive 

 effects of heat ; the first portions of heat 

 applied having most of this resistance 

 opposed to them, their effects are pro- 

 portionably lessened ; while succeeding 

 quantities, having less resistance to 



overcome, produce increased degrees of 

 expansion. The irregularities in the 

 expansion of quicksilver are less than 

 those of any other fluid. 



Count Rumford ascertained the con- 

 traction of water for every 22} in cool- 

 mo; from 212 to 32, the results being 

 as follows : 



In Cooling 22} from 212 or to 189} 18 parts. 



189} 167 16.2 



167 144} 13.8 



144} . 122 11.5 



12-2 99} 9.3 



99* 77 7.1 



77 54} 3.9 



54} 32 0.2 



The very great irregularity at the 

 bottom of the table will be adverted to 

 in considering the remarkable pecu- 

 liarity of water by which it is occa- 

 sioned. It appears by the above table, 

 that the expansion occasioned by heat- 

 ing water 22} nearest the boiling 

 point is almost five times as great as 

 is produced by the heating it 22} 

 from about the natural medium tempe- 

 rature. 



De Luc tried the relative expansibili- 

 ties of a number of different liquids, by 

 putting them into thermometer tubes : 

 the scale which he used was that of 

 Reaumur, upon which 80 indicates the 

 boiling point of water, and the melt- 

 ing point of ice. The results are ex- 

 pressed in the following TABLE, to 

 which are added, by Dr. Ure, the cor- 

 responding indications according to the 

 Centigrade and Fahrenheit Thermo- 

 meters. 



