32 



VOELCKER on the Chemistry of Food. 



On account of these variations, which are often observed 

 in one and the same species of turnips, it is difficult to fix 

 precisely the nutritive value of these roots. The following 

 average analyses must, therefore, be regarded simply as illustra- 

 tions of the proximate composition of some kinds of turnips : 



Proximate average Composition of some kinds of Turnips. 



On an average, turnips thus contain from 89 to 92 per cent, of 

 water, and 8 to 12 per cent, of dry solid matter. Swedes, 

 usually, though by no means always, contain less water than any 

 other variety of turnips ; they are generally firmer and keep 

 better than white turnips. On the whole swedes are more 

 nutritious than other species of this root. In white and yellow 

 turnips the percentage of water is generally higher, and averages 

 90 or 91 per cent. The nutritive value of turnips is often 

 estimated by the amount of nitrogen which they contain. The 

 best roots, however, do not always contain a very high percentage 

 of nitrogen, and it is therefore impracticable to determine the 

 nutritive value of these roots by the amount of nitrogen which 

 they contain. Mr. Lawes, of Rothamsted, indeed, has shown 

 lately in some well-conducted feeding experiments, that those 

 turnips which are richest in nitrogen are by no means the most 

 nutritious. The influence which the soil exercises on the qualities 

 of swedes and turnips is well known to practical men. Thus 

 roots grown on peaty or very stiff clay soils are not near as good 

 as others of the same kind grown on good turnip loam. The 

 climate and season likewise in a remarkable degree affect the 

 qualities of turnips. As these roots succeed best in a moist 

 climate, we can explain why they produce a more abundant and 

 nutritious crop in Scotland than in the south of England. 



Another circumstance which affects the qualities of turnips is 

 the mode of growth. Roots grown rapidly, generally speaking, 

 are not as nutritious, and do not keep so well as turnips, the 

 growth of which is not forced so rapidly by stimulating manures. 



