THE CHEMISTRY OF COOKERY. 219 



Btant propoi'tions in different samples of water. I need not here go 

 into the quantitative details of these proportions, nor the reasons of 

 their variation, though they are very interesting subjects. 



Proceeding with our investigation, we shall find that the bubbles 

 continue to form and rise until the water becomes too hot for the 

 finger to bear immersion. At about this stage something else begins 

 to occur. Much larger bubbles, or rather blisters, are now formed on 

 the bottom of the vessel, immediately over the flame, and they con- 

 tinually collapse into apparent nothingness. Even at this stage a 

 thermometer immersed in the water will show that the boiling-point 

 is not reached. As the temperature rises, these blisters rise higher and 

 higher, become more and more nearly spherical, finally quite so, then 

 detach themselves and rise toward the surface ; but the first that 

 make this venture perish in the attempt they gradually collapse as 

 they rise,- and vanish before reaching the surface. The thermome- 

 ter now shows that the boiling-point is nearly reached, but not quite. 

 Presently the bubbles rise completely to the surface and break there. 

 Now the water is boiling, and the thermometer stands at 212 Fahr. 

 or 100 Cent. 



With the aid of suitable apparatus it can be shown that the atmos- 

 pheric gases above named continue to be given off along with the 

 steam for a considerable time after the boiling has commenced ; the 

 complete removal of their last traces being a very difficult, if not an 

 impossible, physical problem. 



After a moderate period of boiling, however, we may practically 

 regard the water as free from these gases. In this condition I venture 

 to call it cooked water. Our experiment so far indicates one of the 

 differences between cooked and raw water. The cooked water has 

 been deprived of the atmospheric gases that the raw water contained. 

 By cooling some of the cooked water and tasting it the difference of 

 flavor is very perceptible ; by no means improved, though it is quite 

 possible to acquire a preference for this flat, tasteless liquid. 



If a fish be placed in such cooked water it swims for a while with 

 its mouth at the surface of the water, for just there is a film that is 

 reacquiring its charge of oxygen, etc., by absorbing it from the air ; 

 but this film is so thin and so poorly charged, that after a short strug- 

 gle the fish dies for lack of oxygen in its blood, drowned as truly and 

 completely as a living, breathing animal when immersed in any kind 

 of water. 



Spring and river water that have passed through or over consider- 

 able distances in calcareous districts suffer another change in boiling. 

 The origin and nature of this change may be shown by another ex- 

 periment as follows : Buy a pennyworth of lime-water from a drug- 

 gist, and procure a small glass tube of about quill-size, or the stem of 

 a fresh tobacco-pipe may be used. Half fill a small wine-glass with 

 the lime-water, and blow through it by means of the tube of the to- 



