QUANTITY OF NITROGEN JN PLANTS. 67 



branches chiefly consist. The same remark, however, applies to this, 

 as to many other cases which present themselves to the chemist, during 

 his analyses, especially of organized substances, — that those elements 

 which are present only in small quantity are as necessary — as essential 

 — to the constitution of the particular substance in which they occur, as 

 other elements are of which they contain much ; and that if these small 

 (juantities are removed or absent, not only are the physical and chemi- 

 cal properties of the substance materially altered, but it is found also to 

 exercise a very different influence on animal and vegetable life. This 

 latter observation will present itselfto you in a very striking light, when 

 we come hereafter to study the nutritive properties of the several kinds 

 of food by which animals are chiefly suj^ported, — and shall «ee on what 

 elementary body their relative nutritive properties depend, or by the 

 amount of which their relative value appears at least to be indicated. 



But a consideration of the absolute quantity of nitrogen contained in 

 an entire crop will satisfy you that though small in comparative amount, 

 [that is, compared with the carbon and oxygen which plants contain,] 

 this element cannot he without its due share of importance in reference 

 to vegetable life. Hay, as above stated, contains, as it is stacked, 1^* 

 per cent, of nitrogen, or a ton of hay contains 30 lbs. of this element. A 

 good crop of hay, on land which is depastured during the winter, will 

 amount to 2 or 2h tonsf per acre. Taking 2 tons as an average, the hay 

 from one acre will contain 60 lbs. of nitrogen, or from 100 acres 6000 lbs., 

 equal to 2| tons of nitrogen. 



Allowing, therefore, nothing for the aftermath, and supposing the 

 other crops to contain no more nitrogen than the hay does, the farmer of 

 five hundred acres will annually carry into his stack-yard at least 13 

 tons of nitrogen in the form of hay, straw, grain, and other produce, t 



Nature performs all her operations on a large scale, and the quantity 

 of materials she employs are large in a corresponding degree. Hence, 

 though comparatively small, the nitrogen in vegetable substances is ab- 

 solutely large. You cannot suppose, when viewed in this light, that 

 nitrogen is an element of little consequence in reference to vegetable 

 life ; or that in nature it should be so constantly and universally dif- 

 fused without reference to some important end. If I may be allowed a 

 familiar illustration of the mode in which small quantities of matter will 

 affect the sensible properties of large masses, I would recall to your 

 minds the effects of seasoning upon food, in imparting, when added in 

 small quantity only, an agreeable relish to what would otherwise be 



* In different crops of hay Boussingault found in three several years the following pro- 

 portions of nitrogen : — 



Hay, as commonly Hay dried at 



stacked. 260° F. 



In 1836 118 1-04 of nitrogen per cent. 



" 1833 1.3 115 « " 



" 1839 15 1-3 » " 



Aftermath 24 2 " " 



1 The Rev. Mr. Ogle, of Kirkley, Northumberland, informs me that some of his land 

 near the Hall has yielded annually at this rate for 100 years, and without other manure than 

 the droppings from the cattle which have fed upon it. 



X This average estimate gives but an inaccurate idea of the quantity actually contained 

 in some species of crops. Thus red clover with the aid of gypsum will yield 3 tons of hay 

 per acre. This hay contains more than twice the quantity of nitrogen (Boussingault) that 

 common hay does, hence an acre of such hay would contain at least 180 lbs. of nitrogen. 

 (See Lecture II., p. 30.) 



