18 MK. NICHOLS' ADDRESS. 



presenting barriers to the escape of valuable volatile elements, and 

 forming new compounds by the action. If you develope ammonia 

 you must have an acid present to combine with and fix it, in the 

 form of a salt, else it is lost by its extreme volatility, as has been 

 illustrated. In making compost, a grand object is accomplished 

 when such materials are added as will, by chemical change, pro- 

 duce ammonia. For this purpose such substances must be procur- 

 ed as contain nitrogen. 



Decayed flesh, horn shavings, and glue, contain nitrogen, but no 

 ammonia. Now, if you add them to the compost, chemical trans- 

 formation speedily begins, the nitrogen is set free and goes over 

 to the hydrogen, which is always at hand, and ammonia is formed. 

 If this change did not take place either in the compost heap or in 

 the earth after applying it to the soil, they would have no more 

 effect upon crops than bits of lead or iron. The stalk and seeds 

 of plants require nitrogen ; to obtain it, substances in which it is 

 an ingredient must first pass through two chemical changes. They 

 must first be decomposed and ammonia formed ; then the ammonia 

 itself must be decomposed, and thus, through this circuitous path, 

 the plant secures its nitrogen. Substances containing nitric acid 

 are proper ingredients for compost, such as saltpetre, nitrate of 

 soda, rubbish of old clay walls, earth taken from under old build- 

 ings, &c. Substances rich in carbon are easily procured, such as 

 straw, foliage, litter weeds, turf, charcoal dust, &c. To form the 

 seed of grain, substances containing phosphoric acid must not be. 

 omitted, — burnt bones, wood ashes, animal excrement, oil cake, sta- 

 ble manure, &c. 



It would be easy to give recipes, but they are in most cases very 

 unsafe sources of information. The farmer does not want recipes, 

 he must understand principles, and then his guidance will be of 

 that kind which will seldom lead him astray. Some farmers have 

 complained that in their experiments with guano, its application pro- 

 duced the most luxuriant leaves and stalks, but did but little to 

 produce grain. Chemistry teaches that guano is what may be 

 called a quickly forcing manure, being so rich in ammonia that it 

 at once affords a copious supply of nitrogen to the plant, and thus 

 aids prodigiously at the outset in its growth, but is deficient in that 

 •which produces some kinds of grain. If the ground does not con- 



