Bij the same Author. 



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LETTERS on MODERN AGRICULTURE. By 

 Baron YoN LiKBio. Edited bj John Blvth, M.D., Professor of Chemistry, 

 Queen's College, Cork. 



CONTENTS. 



Lkttfr 1.— The conflict between Science and Practical 

 Au-rioulture; The foundation of Airriculturc is ex- 

 iwriencc; Progress founded on exi>erience has its 

 limits ; The connection of Agriculture with Chemis- 

 tiy and the subsequent re-action ; Progress in 

 Agriculture must be based on the Inductive Me- 

 Ihoil ; False Teachers of Agricultural Science; 

 Practice based on the blind exi>erien(-e of others 

 leads to error ; The rejection of scientific teaching 

 by iiraetical men due to their ignorance of the real 

 oliject of Science ; The solution by mere practical 

 men of questions proposed by Agricultural Societies 

 cannot advance Agriculture ; The ryection of all 

 scientific instruction by practical men only leads to 

 self-deception. 



Lett BE 2.— Present profit is the leading principle of 

 the prevailing system of Husbandry ; This system 

 is one of danger to Agriculture; General viewof tlie 

 Nutrition of Plants ; Atmospheric and Mineral 

 Food ; The absolute necessity to I'lauts of all tlie 

 Constituents of their Mineral Food ; Present views 

 of tlie Nutrition of Plants erroneous ; Rain Water 

 does not dissolve out the Mineral Matters in the 

 Soil ; Remarkable absorbent power of Soils for tlie 

 soluble Minend Food of Plants, and particularly for 

 Potash, Ammonia, and Phosphoric Acid ; This 

 power is limited, and varies with the Soil ; Organic 

 matter in the Soil materially modifies this power. 



Letter 3.— Our cultivated Plants do not receive their 

 Food from Solution; Roots of Planta derive their 

 Nourishment only from those portions of Soil ab- 

 sohitely in contact with them ; Tliis view supported 

 by the composition of River, Well, and Drainage 

 Water ; The Roots of Plants must themselves exert 

 Slime peculiar action in Nutrition ; The Life of Laiid- 

 I'lants endangered by Food when in Solution; In 

 Water-plants the laws for the absorption of Food 

 must differ from those of Land-plants ; Tlie Ash of 

 duck-weed shows that Plants have a Power of 

 selecting their Food; Reason why Mud from stag- 

 nant pools is a good Manure ; liemarkable power for 

 absorbing Moisture possessed by Soils ; By absorj)- 

 tioii and evaporation of Moisture the Soil is warmed 

 or cooled ; Great importance of this fact to Vege- 

 tation ; The two .Soirees from which Moisture is 

 ahiiurbeil by the Soil ; Natural Law deduced from 

 the alxive facts. 



Lkttbb L— The Beliefinthe value of Humus no longer 

 exists; its Action now ascertained; Effect of the 

 Salts of Ammonia not dejicndenton their Nitrogen ; 

 1'he action of Nitrates like that of the Salts of 

 Ammonia; Kxperiments with Nitrates and Chlo- 

 riiles; Exiteriments with "-alts of Ammonia alone, 

 and with the addition of Common Salt ; Solubility 

 of the Earthy Phosphates in solutions of Chlorides 

 of Ammonium and of So<liuin, and of Nitrate of 

 Soda; Exjicriments with these Salts : Their Solvent 

 Action similar to that of Carbonic Acid Water; 

 The Salts of Ammonia are decomi>ofied in the .Soil ; 

 their two-fold iction; Ififlerence in the Comport- 

 ment of Salts of Potash and of So<la in the Soil ; 

 I'oliish extracted by Sulphate of Ammonia from 

 Silicates ; Application of the Action of Chili-halt- 

 pctre, S-ilts of Ammonia, and Chloride of .Stxlium 

 to explain the iixrease of fertility in the soil, and 

 the Nutrition of Plants. 



Letter 5.— Nofrce Ammonia in the Soil ; The amount 

 of Food obtained from the Soil by Plants is in pro- 

 portion to the absorbent Root-surfaie : The early 

 development of Roots due to the accumulation of 

 Nourishment in the Surface-soil ; Estimations of 

 the quantity of Ammonia in our cultivated fields ; 

 A deficient crop not due to the Absence of Ammonia 

 in the Soil ; Exjieriments with Salts of Ammonia : 

 the Crops only slightly increased theieby ; Increase 

 of produce due to accoraiianying Minerals; Expe- 

 riments of Lawes and Kuhlmann with Salts of 

 Ammonia, &c. ; The fertility of a field deiiendent 

 on the sum of the Mineral matters in it ; The ac- 

 tivity of these Minerals increased within a given 

 time by the Salts of Ammonia; The Soil more 

 rapidly exhausted by their use, unless there is a 

 restoration to it of the removed Mineral matters. 



Letter 6.- The amount of Carbonic Acid and Am- 

 monia in the Air; The Balance of Organic Life; 

 The Absorption and Assimilation of Food differs iu 

 Perennial and in Annual Plants : The mode of 

 Growth of Perennial, Annual, and Meadow Plants ; 

 The quantity of Nitrogen in different Crops; Ad- 

 vantage of Nitrogenous Manures to Cereals is not 

 in consequence of the failure of Nitrogen from 

 Natural Sources ; Organic and Nitrogenous Ma- 

 nures useful in Annual Plants with small absorbent 

 Leaf and Root-surface ; Effect of Nitrogenous 

 Manures less marki/d in Plants with large Leaf- 

 surface; Supply of Ammonia in Mannte not neces- 

 sary to all Plants ; Green CroiM condense Ammonia 

 from Natural Sources, and supply it in the excre- 

 ment of animals to Corn-fields ; The Nitrogen of 

 Manures is thus indirectly obtained from the Air; 

 The total quantity of Nitrogen from a manured 

 Corn-field is not greiiter tlian from an unnianurcd 

 Meadow, but more time is required by the latter to 

 collect it; Explanation of the good effect of Nitro- 

 gcnised Manures on Annual Plants with small 

 Leaf and Root-surface. 



Letter 7.— Salts of Ammonia increase the number of 

 Roots and Leaves in the first period of the Growth 

 of Plants; hence the superior action of these Salts 

 in Spring; Circumstances which modify the pro- 

 duction of Leaves, Flowers, and Roots; Circuiu- 

 stances under which Nitrogenous and Concentrated 

 Manures are useful ; Causes of the failure of Plants 

 continuously grown on the same Soil; Food of 

 Plants when too concentrated often exerts a dele- 

 terious Chemical action ; Provision in the Soil to 

 Iirevcnt this action ; Properties of .Soils altered In 

 cultivation by the removal of Mineral Matters from 

 them, and by the increase of Organic Matters in 

 them ; The increase of Organic Matter frequently a 

 cause of l)ise;ise ; Finger and Toe Disease- its cure ; 

 Excess of soluble Silica and of hurtful Organic Mat- 

 ter ill soils removed by Lime ; Noxious Organic 

 Matters arising from the continuous growth of 

 Perennial Plants on Meadows removed by Irriga- 

 tion. 



Lkttkr 8.— The food of Land Plants is not absorbed 

 by the roots from Solution, but from the Soil di- 

 rectly in contiu't with them ; Hence the necessity 

 for a uniform distribution of the fiMid of Plants in 

 the Soil, and for the great Ramification of their 

 Roots; A field with much Mineral Food may be 



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