No. VIIL] EXPERIMENTS UPON TURNIPS. G3 



8°. Rape-dust — The results exhibited in this year's experiments, generally, 

 are not so favourable to the employment of this substance as was to be expect- 

 ed. The reason, however, is, probably, that which has already been suggested 

 in discussing the results obtained at Lennox Love — that rape-dust requires a 

 moist soil or occasional showers. But this itself is an important jrrobable deduction. 

 The reader will find a comparative view of the whole of the results with this 

 substance in the text (see Lecture XVII.) 



9°. Animal Charcoal. — The effect of animal charcoal upon Swedes in Mr. 

 Fleming's experiments is only inferior to that of guano. It is certainly deserv- 

 ing of further trials, and especially in comparison with what is called exhausted 

 animal charcoal — that which has already been used in the refining of sugar. 

 In France, the latter is said to be prefen-ed to the former, and to be sold by the 

 sugar refiners at a higher price than they pay for it in the recently prepared 

 state. 



10°. Other mixed manures. — In regard to other mixed manures, the reader 

 will find much practical information by the study especially of No. 3 of Mr. 

 Fleming's tables, p. 45 ; and of Nos. 1 and 2 of those of Mr. Alexander, p. 46. 

 These are the more worthy of the attention of the practical man, since Mr. Flem- 

 ing considers himself justified in remarking as the general result of the experi- 

 ments in p. 45, thai any of the mixtures used will in his land produce an ave- 

 rage crop of turnips at a less expense than fann-yard manure. This is the kind 

 of result which it ought to be the ambition of every practical man to work out 

 for himself upon his own land. 



11°. Size and weight of Jndbs. — There remains only one other topic in con- 

 nection with these experiments to which space will permit me at present to ad- 

 vert. In the remarks upon the table inserted in p. 44, it is stated tliat the tur- 

 nips on the plots dressed with — 



Guano and wood-ashes — were pre-eminent for size of bulbs. 



Sulphate of ammonia — large in buW), bid soft, and light in weight. 



Potash and lime, salt and lime, sulphate of magnesia, nitrate of ^oAsl—sttuUI 



in bulb J but firm and solid. 

 Bone-dust and the artificial guanos — both containing bones — Vie bulbs firm 



OMi soli'i, but not remarkable in siz':. 

 Now upon the solidity of the bulb — other things being equal — it may be pre- 

 sumed that tlie relative nourishing properties of different species of turnip will 

 materially depend. The quantity of water which different specimens of the 

 same variety of turnip contain varies from 79 to 91 per cent. — that is, sovie tur- 

 nips of the same species contain only four-fifths, whi.k others contain upwards of 

 nine-tenths of their weight of wrotcr'. In other words, the same variety of turnip 

 may contain such unlike quantities of water, that 2 tons grown on one spot 

 may not contain more than 1 ton grown in another. The weight of bulbs, there- 

 fore, is no safe criterion of t}ie quantity of food raised on different parts of the 

 same field — where the general treatment, or the substances applied to aid the 

 growth, have been different. 



Now in the above experiments the guano gave 32 tons of very large, the sul- 



fihate of ammonia 24 of soft, and the nitrate of soda 21 of small and solid bulbs, 

 t is probable, therefore, that the actual quantity of food raised by the aid of the 

 nitrate of soda was much greater than even by the natural gueino. It may also 

 have been that the I4j tons of solid bulbs given by the sulphat||of magnesia, 

 or the 12^ raised from the land without manure at all, may have contained as 

 much nutriment as the 24 tons of soft bulbs raised by the sulphate of ammonia. 

 Suggestion IV. — The bare possibility of such a circumstance as the last, 

 shows how little absolute confidence we can place in the numerical results as 

 yet obtained, considered as evidences of the greater or l-ess amount of food, which 

 the use of this or tliat kind of manure will enable us to raise from a given ex- 

 tent of land. It suggests, also, the necessity of a further determination of the 

 relative quantity of water contained in our experimental turnip crops. This 

 will, without difficulty, be effected by selecting three or four turnips of different 



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