1867.] 



Food as a Motive Power. 



335 



total amount of force, the actual energy, which it is capable of pro- 

 ducing when burnt in the body. The materials for this calculation 

 have been supplied by a series of most valuable experiments which 

 have recently been conducted by Dr. Frankland, who published his 

 results in a lecture delivered at the Ivoyal Institution, June 8, 1866. 

 He selected some of the most important articles of food, and burnt 

 one gramme of each of them in a vessel surrounded with water. He 

 noted carefully the extent to which the water became heated; 

 from this it was easy to calculate the calorific value of the food, 

 and from this its work-equivalent in metre-kilogrammes. In the 

 case of nitrogenous foods, such as meat and bread, a certain portion 

 always leaves the body without undergoing oxidation. The calorific 

 value of this residue was determined by Frankland and deducted 

 from that of the food, and we have therefore, for the first time, a 

 trustworthy statement of the actual force-values of these substances. 

 The following table contains a few of the most important figures. 

 A great deal of the enormous differences perceived is due to the 

 different quantities of water which the various substances contain ; 

 but even when they are compared in the dry state, great differences 

 are observed. Fats and oils are superior to all other substances in 

 this respect : — 



Name of Food. 



Actual Energy 

 of 1 gramme as 

 burnt in body. 



Weight and Cost of various articles required 



to be oxidized in tbe body to raise 140 lbs. 



to height of 10,000 feet. 





Metre-kilo- 

 grammes. 



Weight in lbs. 

 required. 



Price per lb. 



Cost. 



Cod-liver oil ... 



Beef fat 



Butter 



Cheshire cheese . 



Oatmeal 



Isinglass 



Lump Sugar .... 



Bread 



Lean beef 



Potatoes 



Cabbage 



3857 



3841 



3077 



1846 



1665 



1550 



1418 



910 



604 



422 



178 



0-553 

 - 555 

 0-693 

 1-156 

 1-281 

 1-377 

 1-505 

 2-345 

 3-532 

 5068 

 12020 



s. d. 

 3 6 



10 



1 6 

 10 

 2| 



16 

 6 



2 



1 

 1 

 1 



s. d. 

 3 H£ 



5£ 



1 0J 

 11| 

 3£ 



22 0£ 

 9 

 4f 

 3 6£ 



5i 



1 0J 



It is curious to compare with these figures the calorific value of 

 coal. The burning of 1 gramme of coal yields an actual energy of 

 2,538 metre-kilogrammes, and we will assume its price to be 25s. 

 per ton. Equal quantities of force can then be obtained by the 

 burning of — 



Coal costing 1*. 



Oatmeal „ 35s. 



Butter „ 125s. or £ 6 5s. 



Lean beef „ 425s. „ 21 5s. 



The food which is the cheapest enumerated as a force producer, is, 



