216 AGRICULTURAL REPORT. [U39U, 39 1 , 392, 393 



and never occurs with the spring derived from the Hgnitic eocene, or the lower 

 cretaceous formation. 



390. formation of Rock — There isar.other effect, due to the same cause, 

 which is frequently observed in the territory of the Omnge Sand formation ; I 

 mean the gradual induration, or trap formation into rock, of strata of sand (11 11) 

 or sandy loam, which have been quite soft within the memory of the inhabitants. 

 When water charged with the carbonate of iron, formed as above mentioned, 

 percolates through strata of sand or gravel, it may come in contact with so much 

 air, contained in the pores of the mass, that its protoxide is reconverted into the 

 yellow peroxide, which adheres to the grains of sand and gradually cements 

 them together into a rock. This takes place more especially, when the iron 

 solution reaches a seam or layer of clay, which prevents it from sinking deeper; 

 a sheet of lerruginous sandstone is then formed on top of the clay. This process 

 may be seen in progress by an attentive observer in almost any region where the 

 Orange Sand prevails, and from the fact that almost all the ledges of ferruginous 

 sandstone found in this formation, are underlaid by a stratum of clay, we may 

 justly conclude that most, if not all this rock has been formed, originally, in a 

 similar manner (H 1 1)- 



391. Nourishment of Plants. — Before entering upon the consideration of the 

 subject of manures, their several kinds and mode of action, it may be well *o 

 recapitulate briefly thj general, well-established principles ol vegetable physiolo- 

 gy, without a knowledge of which, it would be impossible to appreciate correct- 

 ly the bearing of the analyses given below, and to apply to practice in each 

 separate case, the results they contain. 



392. Constituents of Plants. — Most plants, and all, or nearly all, of those 

 wh ch ore the sul ject of the farmer's care, require the same ingredients to be 

 supplied to them fn m the soil and the atmosphere, viz : those which have l*en 

 briefly characterized in the preceding pages, with the sole exception of Alumina 

 (11374), which is not often contained in the ashes of plants (provided they have 

 been thoroughly cleansed of dust, etc., before burning). Fluorine, also, is a 

 very subordinate ingredient, and frequently wanting. — From among the rest, 

 Carbon, Hydrogen, Oxygen and Nitrogen, or rather their combinations, may be, 

 and are for the most part, derived from the air, as has been stated (1T361) ; 

 while the rest of the ingredients required (which are contained in the ashes) 

 are derived from, and must therefore be present in the soil, to support a healthy 

 development of vegetable growth. And experience further proves, that if only 

 & single ode of these ingredients be absent or insufficient in quantity, the presence 

 of all the rest will be unavailing to render the soil productive. To a limited 

 extent, some of these ingredients may be replaced by others of similar chemical 

 character, e. rj. Potash and Soda by each other and by Lime antl Magnesia ; iron 

 by Manganese, etc. Such replacements, however, always cause differences in 

 the mode of development of the plant, and in the quality of the crop. Cultiva- 

 ted plants in particular possess a wider range in this respect, than do those 

 retaining their natural state ; and the consequent adaptability of the vegetables 

 constituting our crops, to a great variety of soils, is a feature of the highest im- 

 portance to the agriculturist. 



393. Rotation. — While, therefore, all plan s require nearly the same ingre- 

 dients so far as their kind is concerned, ea_- i one requires its own peculiar 

 proportion of each of them — varying, in most cases, between narrow limits only. 

 Hen<eit is that, when a soil has been a; parently exhausted by the frequent 

 repi -tiii> n of one. and the s<>me crop, it may Silill be quite productive of another, 

 which find* remaining in the soil a sufficient quantity of available nourishment 

 in the proper relative propoitions required (or its growth. During the season 

 in which the soil has been occupied by the latter crop, the action of the atmos- 

 phere may have set (ret* and rendered available, a fresh supply of nourishment 

 heretofore "locked up" in the undc^mposed minerals of the soil (H356), and 

 in the proportions suitable for the first crop ; which may now again succeed. This 



