624 



FARMERS' REGISTER 



[No. 11 



ihose in the inlerior exposed to the influence of 

 the winds, and liavinij been accustomed to shel- 

 ter, become unheahhy, and die in iheir new situa- 

 tion ; and ti)eii- leaves and branches frradualij' de- 

 composing, produce a siraium of vegetable mat- 

 ter. In many of the great bogs in Ireland and 

 Scoiiand, the larger trees that are found in the 

 out-skirts of tiicm hear the marks ol having been 

 lelled In the interior few entire trees are (bund; 

 and the cause is, probably, that they iell by gra- 

 dual decay ; and that the fermentation and de- 

 composition of the vegetable matter was most ra- 

 pid where it was in the greatest quantiiy. 



Lakes and pools of water are sometimes filled 

 up by the accumulation of ;he remains of aquatic 

 plants; and in this case a sort of spurious peat is 

 formed. The (iirmenlaiion in these cases, howe- 

 ver, f-eems to be of a different kind. Much more 

 gaseous matter is evolved; and the neighborhood 

 of morasses in which aquatic vegetables decom- 

 pose is usually aguish and unhealthy; whilst that 

 of the true peat, or peat formed on soils originally 

 dry, is always salubrious.* 



The earthy matter of peats is uniformly analo- 

 gous to that of the stratum on which they repose; 

 the plants which have formed them must have de- 

 rived the earths that they contained ii-om this stra- 

 tum. Thus in Wiltshire and Berkshire, where 

 the stratum below the peat is chalk, calcareous 

 earth abounds in the ashes, and very little aiumi- 



Fior. 16. 



na and silica. They likewise contain much oxide 

 of iron and gypsum, both of which may be de- 

 rived from the decomposition of the pyrites, so 

 abundant in chalk. 



Difl'erent specimens of peat that I have burnt, 

 from the granitic and schistose soils of different 

 parts of these islands, have always given ashes, 

 principally siliceous and aluminous; and a speci- 

 men of peat from the county of Antrim, gave 

 ashes which aflbrded very nearly the same consti- 

 tuents as the great basaltic stratum of the county. 



Poor and hungry soils, such as are produced 

 from the decomposition of granitic and sandstone 

 rocks, remain very often for ages with only a thin 

 covering of vegetation. Soils from the decompo- 

 sition of limestone, chalks, and basalts, are often 

 clothed by nature with the perennial grasses; and 

 atlbrd, when ploughed up, a rich bed of vegeta- 

 tion lor every species of cultivated plant. 



Hocks and strata from which soils have been 

 derived, and those which compose the more inte- 

 rior solid parts of the globe, are arranged in a cer- 

 tain order; and as it often happens that strata 

 very different in their nature are associated toge- 

 ther, and that the strata immediately beneath the 

 soil contain materials which may be of use for im- 

 proving it, a general view of the nature and posi- 

 tion of rocks and strata in nature will not, I trust, 

 be unacceptable to the scientific farmer. 



Rocks are generally divided by geologists into 



two grand divisions, distinguished by the names 

 of primary and secondary. 



The primary rocks are composed of pure crys- 

 talline matter, and contain no fragments of other 

 rocks. 



The secondary rocks, or strata, consist only 

 partly of crystalline matter, contain fragments of 

 other rocks or strata; often abound in remains of 

 vegetables and marine animals; and sometimes 

 contain the remains of land animals. 



* In tropical climates no peat is fcl-med; the tem- 

 perature is too high. The dead vegetable matter ra- 

 pidly decomposes, and is converted into gases; and 

 this probably is one of the causes of these climates 

 being so much more unhealthy and productive of ma- 

 laria-fevers than temperate and cold climates. — J. D. 



The primary rocks are generally arranged in 

 large masses, or in layers, vertical or more or less 

 inclined to the horizon. 



The secondary rocks are usually disposed in 

 strata or layers, parallel, or nearly parallel, to the 

 horizon. 



The number of primary rocks which are com- 

 monly observed in nature are eight. 



First, granite, which, as has been mentioned, 

 is composed of quartz, feldspar, and mica; when 

 these bodies are arranged in regular layers in the 

 rock, it is called gneiss. 



Second, micaceous schistus, which is composed 

 of quartz and mica, arranged in layers, which are 

 usually curvilineal. 



Third, sienite, which consists of the substance 

 called hornblende and feldspar. 



