DIETARIES UNDER OPPOSITE CIRCUMSTANCES THEIR USES. 499 



as is the phrase that is, effect equal to the raising of so many 

 pounds' weight one foot in a man's full day's mechanical 

 work is 792,000 ; while he states that this work may reach 

 1,500,000 foot-pounds when the labour is pushing or driving 

 horizontally that is, near a fourth part of the whole work at 

 the highest estimate above stated. A medium number would 

 have better suited our purpose viz., the inferring what belongs 

 to a horse in this respect, from what is ascertained as to a man. 



We have chosen the above mode of giving an outline of this 

 very important speculation, as sufficient to make the subject 

 intelligible, in preference to attempting to follow out Professor 

 Playfair's method of proceeding, for which we must refer to 

 the three memoirs indicated below.* Professor Play fair ex- 

 amines dietaries of known authority adapted to men under 

 very opposite circumstances as for convalescents in hospitals 

 after acute diseases, that of the inmates of prisons, that of 

 soldiers during peace, that of soldiers during war, that of the 

 Koyal Engineers, and that of labourers under severe exertions; 

 and from these he deduces not only how much carbon each 

 diet contains, but also what are the relative proportions in 

 each of flesh-giving material and calorific material. Then, 

 choosing out several standard dietaries, one for each class of 

 persons, he tries other dietaries by the standards corresponding 

 to these other dietaries. In this way he produces information 

 of the most important kind, particularly as respects the neces- 

 sary proportion between the flesh-giving materials and the cal- 

 orific materials under different circumstances of life. 



The proportion of carbon in his several dietaries bears a 

 material reference to the view exhibited above as to the amount 

 of carbonic acid thrown off daily in respiration. In some of 



* Play fair, Lecture at the Royal Society, Edinburgh, and at the Royal 

 Institution, London ; Memoir 1, ' Good Words, ' January 1853; Memoir 2, 

 'Good Words,' February 1865. 



