208 agricultural report. [1361, 362, 363, 364, 365, 366 



361. Important Combinations. — Theso elements, in their combinations 

 amongst themselves, and especially with Oxygen, compose the vast majority 

 of all material objects that surround us. The human frame ordinarily contains 

 every one of them ; and so do most plants (if we except Fluorine and 

 Aluminium'). The first four, in combination, form the great bulk of vegetables, 

 such as wood, starch, albumen, etc. Oxygen and Hydrogen form Water ; 

 Oxygen and Carbon, Carbonic Acid Cthe gas contained in soda-water) ; Hydrogen 

 and Nitrogen, Ammonia (spirits of hartshorn). Air is a mixture of four-fifths 

 (by bulk) of Nitrogen and one-fifth of Oxygen ; it always contains, at the same 

 time, variable amounts of Aqueous Vapor, and minute quantities of Carbonic- 

 Acid (one three-thousandth) and Ammonia (between one and two millionths). 



Small and insignificant as the amounts of the two latter ingredients present 

 in air may appear, they perform most important parts in vegetable economy. 

 All the carbon which plants contain is obtained by them from the atmosphere in 

 the shape of carbonic acid, which they decompose, retaining the carbon and 

 returning the oxygen to the atmosphere. In the same manner, a large portion 

 of the nitrogen contained in plants, is derived from the ammonia present in the 

 air ; while their fixed mineral ingredients, which remain behind in the shape 

 of ashes when vegetables are burnt, are derived from the soil. 



362. The combinations of other elements with oxygen (which are produced 

 by burning the same), are called Oxides ; a large part of these, generally 

 possessing a sour taste, are called Acids. Thus we have Oxide of Iron, of 

 Manganese ; Sulphuric, Phosphoric, Carbonic acid, etc. Combinations of Oxides 

 and Acids are called Salts. 



The combinations of the other elements, most important to the agriculturist 

 are the following : 



363. Silicon — with oxygen, forming Silica — flint, quartz, rock crystal, the 

 hard grains of almost all sands ; in the latter form, and in combination with 

 Alumina, it forms the great bulk of most soils. Moreover, it enters largely into 

 the composition of all grasses, of pine straw, and a great number of other plants. 

 It is but seldom that soils are deficient in silica as such; but it often happens 

 that it is not present in an available, or soluble, condition ; a defect promptly 

 remedied by the application of lime. 



364. Sulphur — with ogygen, forming Sulphuric acid (in its pure state called 

 oil of vitriol) ; this in combination with Lime, forms Gypsum, or plaster of 

 Paris ; with Magnesia, Epsom Salt ; with protoxide of Iron, Copperas, etc. 



365. Phosphorus (well-known as the inflaming ingredient of common frictiom 

 matches) with oxygen forms Phosphoric acid. The latter, in combination witk 

 Lime, forms the earthy part of bones, or bone-ash, which is, essentially, 

 phosphate, with a little carbonate, of lime. Phosphoric acid is, moreover, con- 

 tained in all seeds, to a considerable amount ; hence, its absence from the soil 

 is fatal to the formation of seed of any kind. The stem and leaves of plants 

 require it also, but in much smaller quantities. 



366. Potassium and Sodium, form with oxygen, repectively, Potash (the 

 potential caustic of druggists) and Soda; the former, in combination with car- 

 bonic acid, is the chief ingredient of pearlash, saleratus, etc. ; while the combi- 

 nations of soda with the same acid, are what are familiarly know to our house- 

 keepers as soda, or salsoda. Moreover, sodium in combination with chlorine, 

 forms common salt. — Potash is as universally required by all plants (excepting 

 sea- weeds) as phosphoric acid, and is therefore one of the most important and 

 indispensable ingredients of a good soil ; so much so, that the amounts of potash 

 and phosphoric acid contained in a soil, may usually, in practice, be taken as a 

 direct index of its fertility. All other ingredients necessary for the growth of 

 plants are more easily and more cheaply supplied, than these two. Whenever 

 they are wanting, or are present in very minute quantities only, we may consid- 

 er, for all practical purposes, that the soil has to be made before it will produce 

 anything. 



