248 



FARMERS' REGISTER. 



[No. 



to preserve as complete a level as possible, that 

 there are actually no less than ttcenty tunnels be- 

 tween the two termini. One of these is a mile in 

 lenirth, while another, which is half a mile long, 

 is carried under the bed ot" a river which crosses 

 the line. — Mechanics^ Mascazlne. 



GEOLOGICAL ORIGIN AND FORMATION OF 

 SOIL. 



Extract from Dr. C. T. Jackftnn^s Geological 

 Survey of part (f JSIa'ine. 



Every attentive person must have observed, 

 that solid rocks, exposed lo the combined action of 

 air, water, and difierent deijrces of temperature, 

 undergo decomposition and disintegration, so that 

 they crumble into powder, and that some rocks 

 decay more rapidly than others, owing to their 

 structure, or mineralofrical composition. If a rock 

 is porous, or stratified in its structure, water infil- 

 trates into it, and on ti-eezin<r, expands with such 

 power as to tear the surface of the rock to pieces, 

 so that it readily crumbles. When fire runs 

 through the forests, it heats the surlace of the 

 rocks, and by the irregular expansion produced, 

 they are shivered into fraixments. 



The action of runnino; water and friction of 

 stones, also serve to grind the rocks into powder, 

 by attrition of tneir surfaces, and the detritus is 

 iborne along by the streams, and deposited in low 

 Jands, or along their borders. 



When a rock contains iron pyrites, or sulphuret 

 of iron, that mineral, by the action of air and wa- 

 ter, decomposes, and forms copperas, or sulphate 

 of iron, and the sulphuric acid of that substance 

 acts powerfully on some of the ingredients of the 

 rock, and causes its rapid decomposition. Any 

 person, who has been on Iron Mine Hill, in Gar- 

 diner, will fully understand how rapid is this ope- 

 ration, and may there see its results. The oxidiz- 

 ing power of the atmosphere, also, acts power- 

 fully upon the surface of those rocks, which have 

 for one of their components, the prot-oxides of the 

 metals, iron and manganese, and as those oxides 

 take up another portion of oxygen, they increase 

 in bulk, become brown or black, and the stone falls 

 into fragments. 



These are a few of the causes now in action, 

 which modify the solid crust of the globe, and it 

 appears that their effects are far more important, 

 than we might at first imagine. Whoever looks 

 upon the muddy waters of the Mississippi, Gan- 

 ges, Po, the Rhine, and the Rhone, or reads the 

 calculations respecting the enormous quantity of 

 matter brought down from the mountains by those 

 rivers, will at once appreciate the modifyintr influ- 

 ence of those causes which are continually wear- 

 ing down the solid matter that forms the mass of 

 our mountains. 



Geology teaches us, that such causes were ftr- 

 merly in more powerfijl operation, and that the an- 

 cient world was, from its infancy, subject to vio- 

 lent catastrophes accompanied by powerful in- 

 roads of the sea; oceanic currents and tumultuous 

 waves having for many successive periods rushed 

 over the land, and beaten the loftiest crags of the 

 highest mountains. We should then naturally 

 expect, that the earth would present ample testi- 

 mony of the action of these powerfial causes of 



disintegration of the rocks, and' we do observe 

 that a large portion of the loose materials upon 

 the surface, bears proofs of aqueous action and 

 mechanical abrasion. By those ancient convul- 

 sions, the detritus of the solid rocks was prepared, 

 and forming the various soils, which we observe, 

 the earth was rendered capable of yielding its rich 

 stores of vegetation, on which a lar^e proportion 

 of the animated creatures depend for their food. 

 From the Ibundation of the everlasting hills, the 

 Creator began to prepare the world for the habita- 

 tion of his noblest creature, man, and converted a 

 portion of the solid rocks into soils, which were 

 given as the field of human lalior, and to the pro- 

 genitor of our race it was commanded that he 

 should till the soil. 



It we take up a handful of earth, and examine 

 it attentively, we shall readily discover such mine- 

 ral ingredients, as denote the rocks from which it 

 originated. Thus we discover in a soil numerous 

 spangles of mica, grains of quartz, and white or 

 brown earthy looking particles, which are felspar ; 

 besides which, we remark a considerable portion 

 of fine brown powder, which being examined 

 with a microscope is fo md to be composed of the 

 same minerals, more finely pulverised, and mixed 

 with the brown oxide of iron. It will be at once 

 understood, that such a soil arises from the disin- 

 tegration and decomposition of granite rocks, and 

 that the oxide of iron was derived from the py- 

 rites, or the prot-oxide of iron, contained in that 

 rock. 



A soil arising from the decomposition of gneiss, 

 possesses similar characters, only the mica is more 

 abundant. 



Soils from mica slate are made up of a large 

 proportion of mica, mixed with grains of quartz. 



Sienite, and hornblende rock produce a dark 

 brown soil, in which there is but little quartz, and 

 a great deal of felspar, and decomposed horn- 

 blende. 



Greenstone trap rocks form, by their decompo- 

 sition, a brown soil, which contains pieces of the 

 undecomposed rock, but the component minerals 

 in the soil itself, are rarely so distinct as to be dis- 

 coverable. This soil is a warm kind of loam, soft 

 and spongy, easily compressed into smaller di- 

 mensions by the pressure of the hand, but not ad- 

 hesive like clay. It is peculiarly adapted to the 

 growth ofpotatoes. and is a luxuriant soil lor most 

 of our ordinary produce. 



Slate-rocks form a soil of a blue color, in which 

 numerous undecomposed fragments of the rock 

 may be discovered. When transported by water, 

 it is deposited in the state of tough blue clay. 



Limestone forms various colored soils, according 

 to the nature of the impurities it contains. They 

 are generally of a light yellowish brown color, 

 from admixture of a certain proportion of oxide of 

 iron. This is especially the case with those soils 

 derived from the arfrillo-ferruginous limestone. 



Calcareous soils, if they are rich in carbonate of 

 lime, may be distinsiuished by their effervescence 

 with acids, and the quantity of this substarice 

 may be estimated by the loss of weight which in- 

 dicates the proportion of carbonic acid, that has 

 been expelled, and since the carbonic acid always 

 occurs in the ratio of nearly 44 per cent, to 56 per 

 cent, of lime, it is easy, by a proportional calcula- 

 tion, to ascertain the "quantity of that mineral in 

 the soil. 



