218 THE POPULAR SCIENCE MONTHLY. 



not, when eaten by ordinary mortals, do so much nutritive work. 

 Why is this ? 



It is a matter of preparation not exactly what is called cooking, 

 but equivalent to what cooking should be. It is the preparation which 

 has converted the grass-food of the ox into another kind of food 

 which we can assimilate very easily. 



The fact that we use the digestive and nutrient apparatus of sheep, 

 oxen, etc., for the preparation of our food is merely a transitory bar- 

 barism, to be ultimately superseded when my present subject is suffi- 

 ciently understood and applied to enable us to prepare the constitu- 

 ents of the vegetable kingdom in such a manner that they shall be 

 as easily assimilated as the prepared grass which we call beef and 

 mutton, and which we now use only on account of our ignorance of 

 " The Chemistry of Cooking." 



II. THE BOILING OF WATEE. 



As this is one of the most rudimentary of the operations of cook- 

 ery, and the most frequently performed, it naturally takes a first place 

 in treating the subject. 



"Water is boiled in the kitchen for two distinct purposes : 1. For 

 the cooking of itself ; 2. For the cooking of other things. A disser- 

 tation on the difference between raw water and cooked water may 

 appear pedantic, but, as I shall presently show, it is considerable, very 

 practical, and important. 



The best way to study any physical subject is to examine it experi- 

 mentally, but this is not always possible with every-day means. In 

 this case, however, there is no difficulty. 



Take a thin * glass vessel, such as a flask, or, better, one of the 

 " beakers," or thin, tumbler-shaped vessels, so largely used in chemical 

 laboratories ; partially fill it with ordinary household water, and then 

 place it over the flame of a spirit-lamp, or Bunsen's, or other smoke- 

 less gas-burner. Carefully watch the result, and the following will be 

 observed : First of all little bubbles will be formed, adhering to the 

 sides of the glass, but ultimately rising to the surface, and there be- 

 coming dissipated by diffusion in the air. 



This is not boiling, as may be proved by trying the temperature 

 with the finger. What, then, is it ? 



It is the yielding back of the atmospheric gases which the water 

 has dissolved or condensed within itself. These bubbles have been 

 collected and by analysis proved to consist of oxygen, nitrogen, and 

 carbonic acid, obtained from the air ; but in the water they exist by 

 no means in the same proportions as originally in the air, nor in con- 



* In applying heat to glass vessels, thickness is a source of weakness or liability to 

 fracture, on account of the unequal expansion of the two sides, due to inequality of tem- 

 perature, which, of course, increases with the thickness of the glass. Besides this, the 

 thickness increases the leverage of the breaking strain. 



