4J6 



CHEMISTRY. 



[ Mi NCR EM. 



SOex ..... AJ in Sand. 



Alumina .... Clay. 



LioM ..... ,, Clialk and limestone. 



Oxide of iron . . Sand and clay. 



Phosphorus ... ,, Phosphate of limo. 



R..I k., in Pl*ter of ParU (sul- 



Sulphur . . . . | phate of lime). 



->gcn .... ,, Ammonia. 

 ., . ( Chalk, carbonic acid, 



xm ( vegetable matter, dw. 



The followingsnpplv some or all of these substances : 

 rayt.Tbit abounds i 



in every town, and has 



frequently been utilised to a great extent Near Edin- 

 !i there are fields which, from being comparatively 

 worthless, now produce several crops of grass annually, 

 owing to the sewage of the city being allowed to flow over 

 them. Generally speaking, however, sewage matter is 

 far too much diluted with water to be of much value, 

 except in places where it can be readily applied by pump- 

 >r the natural fall of the land. Of course it contains 

 very substance required on the land, because it is the 

 product of all that has been taken from the land in the 

 shape of corn, grass, and the flesh of oxen, sheep, &C., 

 fed on it. When it can be economically applied, it is 

 hi-.'hly valuable ; but on clayey grounds, the immense 

 amount of moisture deposited may prove hurtful. On 

 sandy soils it becomes a most eligible manure. 



2. Guano. This substance is in high repute. It con- 

 tains nitrogen (as ammonia), phosphorus (as phosphate 

 of lime), silex, lime, <tc. Indeed, we may consider it as 

 the concentrated equivalent of town sewage. It is com- 

 posed of the decomposed excreta, feathers, bones, etc., 

 of birds. 



3. Artificial Manures. Next to the above come a 

 legion of manures prepared artificially, all resembling 

 sewage matter and guano, and containing the elements 

 to which we hare referred. To enumerate such would be 

 impossible. Some are of great value ; and in many we 

 are inclined to believe that the only thing of value about 

 them is the cask in which they are contained. Of such, 

 we say to the farmer Caveat Emptor. 



4. Super-phosphates. These manures are made by cal- 

 cining bones, and adding sulphuric acid thereto. A 

 super-phosphate of lime with sulphate of lime is pro- 

 duced, affording phosphorus, sulphur, and lime. These 

 are generally sold as bone manures, and are of great 

 value to most soils. 



5. Lime, Chalk, Limestone, Some lands require the 

 destruction of vegetable matter, which is effected by the 

 addition of 



6. Caustic Lime.. This may be readily obtained by 

 burning chalk, which drives off the carbonic acid. 

 Chalk gives soft, and limestone hard, lime. Chalk or 

 limestone is eligible for lands deficient of lime, but not 

 requiring that substance for the purposes just named. 

 They graduvlly become soluble, by the absorption of car- 

 bonic acid from the atmosphere. 



7. Fuk, Seaweed, <tc. These are readily procurable 

 at the sea-side, and contain lime, common salt, and many 

 other substances. They are each spread broad-cast on 

 the land, or heaped up that they may putrefy. In Kent 

 tliis manure is largely used ; and sometimes sprats are 

 so plentiful on the south coast of England, that they are 

 employed to a very great extent by the farmers. 



In the above epitome of manures, we have not in- 

 cluded stable dung, human excreta, etc. The latter is 

 used almost exclusively in China, and we need scarcely 

 say is highly valuable. It is dried and made into cakes, 

 in which form it is sold to the agriculturist in that 

 country. 



We have, in these observations on the subject of Agri- 

 cultural Chemistry, confined ourselves solely to the results 

 of personal experience in most parts of Great Britain 

 and Ireland. We have met and conversed with farmers of 

 every degree of intelligence and experience, and must say, 

 that to depend on the dicta of any one or any class, would 

 be to go counter to the rules of sound farming. What 

 would be excellent as a plan in the south of England, 

 would bring starvation to the doors of a northern farmer. 

 In Ireland things spring up despite human intelligence ; 

 in Scotland, in despite of nature ; and in England, these 

 extremes meet. But the progress of science and rail- 

 roads is effecting immense revolutions. Agricultural 

 societies present to their members the results of extended 

 experience and observation ; the suns of farmers are 

 now almost universally acquainted with, or are being 

 instructed in chemistry ; and the " dark ages" of agricul- 

 ture are passing away into the things that were. 



Of course we have only given a sketch of the application 

 of chemical science ; we shall conclude by recommending 

 the perusal, by such of our readers as may need greater 

 detail, of the works of Davy, Liebig, Johnston, and other 

 eminent men, to whom humanity will ever owe a lasting 

 debt of gratitude. The Proceedings of the Royal A 

 cultural Societies also afford much valuable information 

 to the practical farmer on all the points we have named. 



CHAPTER XIII. 

 THE SANITARY APPLICATIONS OF CHEMISTRY. 



NOTHING: is more gratifying to the true philosopher than 

 to find that the facts and laws he has discovered may be 

 applied for the social benefit of mankind ; and just in 

 proportion a* thu is successful, so he gains the reward of 

 hi* labours. 



Of late yean, the subject of Social Science has been 

 extensively ventilated ; and, under the able and active 

 superintendence of Lord Brougham, an association has 

 been formed, with the object of discussing all questions 

 relating to the moral, mental, and physical well-being of 

 our nation. It is with the last department, in iU rela- 

 tion to chemical science, that we shall briefly deal 



Health, individually and socially, depends chiefly on 

 an abundant supply of fresh air, good (not "pure") 

 water, and wholesome food. The latter is assimilated 

 with the animal system ; the water assists in diluting the 

 food, in iU assimilation, and in the fonnation o? the 

 blood, flesh, bone*, <tc., conveying the soluble matter* 

 to their proper destination ; whilst the air, acting on the 

 carbon of the food, causes its slow combustion, and this 

 affords heat to the animal 



We, however, necessarily give off, in our most healthy 

 condition, various excreta, consisting of gases, liquids, 

 and solids ; of which the chief are, carbonic acid from 

 the breath and skin, other gases the product of digestion, 

 dec., urine, and f icces ; all of which, whilst decidedly 

 poisonous to humanity, are extremely valuable as food 

 for plants. In other words, what we have done with 

 and must get rid of, is exactly that which the vegetable 

 kingdom must have, and hence arises a compensating 

 process between animal and vegetable life and their 

 exigencies. The subject has already been entered into 

 in the last chapter ; we shall, therefore, not require to 

 describe the uses of animal products. In dealing with 

 this subject, we shall confine our remarks almost solely 

 to the question of pure air ; for the supply of water and 

 the adulteration of food have already become subjects of 

 government interference, and may be safely left to 

 public management. Our supply of air, on the con- 

 trary, is purely a penonal question, and so deserves the 

 most careful consideration. 



During the process of respiration, carbonic acid is 



