LIE BIG'S SCIENTIFIC ACHIEVEMENTS. 



71 



observed this property of the soil and other po- 

 rous bodies ; but neither they nor Liebig had 

 hitherto turned it to account in agriculture; it 

 must have been deemed injurious rather than 

 beneficial, beeause it had been held that what was 

 wanted was to make the nourishment in the soil 

 not insoluble but soluble. It was to Liebig that 

 the principle first occurred that the soil, like 

 water, only just in the reverse way, could be 

 saturated with matters to a certain extent without 

 chemically combining with them ; that as, for in- 

 stance, common salt in water becomes fluid, and 

 mixes with it without altering its nature, or chemi- 

 cally combining with it, so the nourishing mineral 

 matters dissolved in water again become solid in 

 contact with earth, and go into the earth without 

 change in their chemical composition. Liebig 

 perceived now that land-plants extract the mat- 

 ters by means of their roots from the soil which 

 the soil has abstracted from water and rendered 

 insoluble. 



He now saturated unfruitful peat-earth with 

 mineral matters containing nourishment for 

 plants. Water filtered through such earth ab- 

 stracted nothing from it whatever, but grain, 

 peas, beans, etc., flourished luxuriantly, and bore 

 over one hundred - fold. Their delicate roots 

 could abstract what water could not. 



Liebig knew now why his mineral manures 

 produced little or no effect. With great chem- 

 ical shrewdness he had rendered certain sub- 

 stances, particularly potash and the phosphates, 

 almost insoluble in water, and prevented them 

 from passing into the absorbent soil. When he 

 perceived his mistake, it was as if scales had 

 fallen from his eyes : he saw clearly before him 

 the end at which he had so long been aiming. 



In 1862 his great work, in two volumes, ap- 

 peared : " The Chemical Process of the Nourish- 

 ment of Plants and the Natural Laws of Agri- 

 culture." By this Liebig completed and crowned 

 his science of agriculture ; his doctrines are now 

 everywhere acknowledged, and no thoughtful 

 farmer supposes that he has only to lay on super- 

 phosphate, nitrogen, or guano, to make his fields 

 fruitful forever. The object is now to apply Lie- 

 big's theories by the best methods. The Ger- 

 man land-owners gratefully acknowledged this a 

 few years ago by founding the Liebig Institute. 



How deep was the impression made upon 

 Liebig's mind by these discoveries is clearly 

 shown by his own words. He says in his intro- 

 duction to his work of 1862 : 



" It was a real and perpetual grief to me that I 

 could not discover why the effect of my manures 



was so tardy ; I saw everywhere, in thousands of 

 cases, that every one of their component parts 

 produced its effect alone, yet when combined, as in 

 my manures, they produced none. 



" At last, three years ago, after submitting all 

 the facts, step by step, to fresh and careful experi- 

 ment, I discovered the reason. I had sinned 

 against the wisdom of the Creator and suffered 

 just punishment. I thought to improve upon his 

 work, and fancied, in my blindness, that in the 

 wondrous chain of laws by which life is ever 

 maintained and renewed on the surface of the 

 earth, one link was wanting which I, a weak and 

 helpless worm, was to supply. It had, however, 

 been provided for ; but in so wonderful a manner 

 that the existence of such a law had hitherto been 

 unsuspected by man's intelligence, numerous as 

 were the facts that indicated it ; but facts, though 

 they speak truth, are dumb, or one hears not 

 what they say, when error drowns their voice. So 

 it was with me. The alkalies, I thought to my- 

 self, must be made insoluble, or the rain will 

 carry them off! I did not then know that the 

 soil holds them fast, so soon as solutions of them 

 come into contact with it, for the law to which 

 my experiments in agriculture have led is as fol- 

 lows : Organic life is developed on the crust of 

 the earth under the influence of the sun, and the 

 great Architect gave to the ruins of this crust 

 the property of attracting and holding fast all 

 those elements which serve for the nourishment 

 of plants, and thereby of animals also, as the mag- 

 net attracts and holds fast iron filings, so that no 

 particle is lost. The Creator included in this an 

 other law, whereby the earth, bearing plants, is 

 a vast cleansing apparatus for water, from which 

 by this property it removes all those matters which 

 would be injurious to man and beast, the products 

 of the decay of generations of plants and ani- 

 mals." 



In glancing at Liebig's influence on animal 

 physiology, I shall be more concise, as his meth- 

 od of procedure did not differ from that with 

 agricultural chemistry. In this department also 

 his studies were based upon exact organic chem- 

 istry. What first attracted him was the reception 

 of organic nourishment and the reversed meta- 

 morphosis of matter under the influence of oxy- 

 gen from the highly complex to the simple, to the 

 inorganic, from albumen and fat to uric acid and 

 urea, carbonic acid, water, ammonia, and ashes, 

 just as he had pursued the reverse method with 

 plants. The researches into the changes in uric 

 acid under the influence of oxidation may be re- 

 garded as thoroughly typical of his work ; like 

 the researches into benzoin, it was undertaken in 

 conjunction with his friend Wohler, who ten years 

 before had succeeded in making a synthesis of 



