CO^'CLUDING SECTION. 61«3 



theoretical and of a practical kind, that bad my limits peniiii.ted 1 could 

 have wished to dwell upon them at still greater length. 



§ 18. Concluding Section. 



I have now brought the subject of these Lectures to a close. I have 

 gone over the whole ground which in the outset I proposed to tread. It 

 is the first time, I believe, that much of it has been trodden by scientific 

 men, and I have endeavoured in every part of our journey to lay before 

 you, as clearly as I could, everything we knew of the country we passed 

 over, in so far as it had a practical bearing or was likely to be suscepti- 

 ble hereafter of a practical application. 



In the first Part, I directed your attention to the organic portion of 

 plants — showed you of what substances it consisted — on what kind of 

 organic food plants live — and by what chemical changes the peculiar 

 organic compounds of which they consist are formed out of the organic 

 food on which they live. 



In the second Part, I explained in a similar way the nature, composi- 

 tion, and origin of the inorganic portion of plants. I dwelt, also, upon 

 the nature, origin, and natural differences which exist among the soils on 

 which our crops are grown, and from which the inorganic constituents of 

 plants are altogether derived. This led me to explain the connection 

 which exists between Agriculture and Geology, , and the kind of light 

 which this interesting science is fitted to throw upon the means of prac- 

 tically improving the soil. 



In the third Part, I dwelt upon the various means which may be 

 adopted for increasing the general productiveness of the land — whether > 

 these means be of a mechanical or chemical nature. The >|j^le doc- 

 trine of manures was here discussed and many suggestions offered to 

 your notice, which have already led to interesting practical results. 



In the fourth Part, I have explained the chemical composition of the 

 several kinds of vegetable produce which are usu'ally raised for food — 

 showed upon what constituents their nutritive values depend — and how 

 soil, climate, and manure affect their composition and their value as 

 food. The nature and composition of milk and of its products — butter 

 and cheese — the theory of their manufacture, and the circumstances upon 

 which their respective (juantities and (jualities depend — and, lastly, the 

 way in which food acts upon and supports the animal body, and how the 

 value of the manures they make is dependent upon the purpose for 

 which the animal is fed — these subjects have also been considered and 

 discussed in this fourth Part. 



In discussing new topics I have had occasion to bring before you many 

 new views. This, however, I have not done lightly or without consi- 

 deration, and I feel it to have been one of the greatest advantages which 

 have attended the periodical form in which these Lectures have been 

 brought before the public, that it has allowed me leisure to think, to in- 

 quire, and to make experiments in regard to points upon which it was 

 difficult at first to throw any satisfactory light. It is gratifying to me to 

 know that the general difflision which these Lectures have obtained, has 

 already done some service to the agriculture of the country. 



