2i8 THE POPULAR SCIENCE MONTHLY. 



trembling ; may grow rhubarb and make pies and puddings in defiance 

 of the agent. When this is the case, his craving for potato-potash 

 will probably diminish, and his children may actually feed on bread. 



As regards the nutritive value of the potato, it is well to under- 

 stand that the common notion concerning its cheapness as an article of 

 food is a fallacy. Taking Dr. Edward Smith's figures, 760 grains of 

 carbon and 24 grains of nitrogen are contained in one pound of pota- 

 toes ; two and one half pounds of potatoes are required to supply the 

 amount of carbon contained in one pound of bread ; and three and 

 one half pounds of potatoes are necessary for supplying the nitrogen 

 of one pound of bread. With bread at three halfpence per pound, 

 potatoes should cost less than one halfpenny per pound, in order to 

 be as cheap as bread for the hard-working man who requires an 

 abundance of nitrogenous food. 



My own observations in Ireland have fully convinced me of the 

 wisdom of William Cobbett's denunciation of the potato as a staple 

 article of food. The bulk that has to be eaten, and is eaten, in order 

 to sustain life, converts the potato-feeder into a mere assimilating ma- 

 chine during a large part of the day, and renders him unfit for any 

 kind of vigorous mental or bodily exertion. If I were the autocratic 

 Czar of Ireland, my first step toward the regeneration of the Irish peo- 

 ple would be the introduction, acclimatizing, and dissemination of the 

 Colorado beetle, in order to produce a complete and permanent potato- 

 famiiie. The effect of potato-feeding may be studied by watching 

 the work of a potato-fed Irish mower or reaper who comes across to 

 work upon an English farm where the harvest-men are fed in the 

 farm-house and where beer is not excessive. The improvement of his 

 working powers after two or three weeks of English feeding is com- 

 parable to that of a horse when fed upon corn, beans, and hay, after 

 feeding for a year on grass only. 



The reader may have observed that the starch-foods already de- 

 scribed are all derived from the roots or stems of plants. Many 

 others might be named that are used in tropical climates where little 

 labor is demanded or done, and but little nitrogenous food required. 

 Having treated the cookery of the chief constituents of these parts of 

 the plant, the fiber and the starch, I now come to food obtained from 

 the seeds and the leaves. 



Taking the seeds first, as the more important, it becomes necessary 

 to describe the nitrosrenous constituents which are more abundant in 

 them than in any other part of the plant, though they also contain the 

 starch and cell material, or woody fiber, as already stated. 



In No. 29 of this series, page 65, I described a method of sepa- 

 rating starch from flour by washing a piece of dough in water, and 

 thereby removing the starch-granules, Avhich fall to the bottom of the 

 water. If this washing is continued until no further milkiness of the 

 water is produced, the piece of dough will be much reduced in dimen- 



