NOTES. 463 



agues. A column of water of this description may occupy a space of many miles 

 extent between b and a ; and c may be many hundred feet deep below the hori- 

 zontal level of a. In digging for water at d, we should find it at e. 



The cohesion of the particles of water, and its extreme facility to obey any 

 impression, fit it admirably for percolating through fissures of the earth, when in 

 the tenderest filaments it is detached from the general fluid mass, and penetrates 

 only by the laws of capillary attraction from one point to another in an extensive 

 stratum of clay, precisely as if it flowed through a pipe in passing from one hill to 

 another. Hence the certainty with which we meet with water in boring to a 

 proper depth in the earth, and hence also the origin of Artesian wells, which finely 

 expound the varied phenomena of a retreating and subsiding column towards the 

 body of the fluid, as if an equal and opposite pressure from the sides of a capillary 

 tube had come into action. We may hence infer, that in strata pervious to water, 

 the capillary ascension, however much it may be accelerated or retarded by the 

 parallel sides of the stratum and the material of which it is composed, is governed 

 by these three principles which we have fully discussed, pressure from above, 

 cohesion subsisting among the particles of the liquid, and attraction of the parallel 

 sides of the stratum. Were this attraction equal to the antagonist cohesion, the 

 fluid would remain at rest, balanced at a common level, till overcome by the weight 

 of the contents in the longer branch of the fluid column forcing the contents of the 

 shorter column out at the discharging orifice. All the springs which are below the 

 London clay, at the depth of 150, 200, 250, or 300 feet, are fed by sources con- 

 siderably elevated above the Hampstead level. With what ease then might the 

 metropolis be provided in every street with spring water from an Artesian Well ! 



Any of our readers who may be desirous of acquiring a practical and thorough 

 knowledge of geology, must chiefly prosecute his studies by laborious researches in 

 the great field of nature, and must there explore for himself the various phenomena 

 presented to his view. His first step must be to understand by reading the leading 

 facts and principles of the science ; he must learn to recognise at once the principal 

 simple minerals, entering into the composition of rocks, and also the various 

 metallic ores and other minerals which usually occur in veins. He must likewise 

 be acquainted, the more minutely the better, with at least the more common forms 

 of fossil organization, and with the general mode of their distribution in the rocky 

 masses constituting the crust of the globe. Some preliminary knowledge of 

 chemistry, although not perhaps essential, will form a very desirable addition to 

 the qualifications already named. Thus provided with the knowledge requisite 

 to decipher the instructive pages on which nature has recorded, in her own 

 language, the history and revolutions of our planet, the student may now com- 

 mence the most valuable, but far the most laborious part of his career. He must 

 visit the deep recesses of our mines, which, although too much neglected, afford 

 the finest examples of many of the most important facts on which the science of 

 geology is built. He must observe the strata as laid open in our quarries, and as 

 displayed in the deep cuttings of our roads, railways, and canals. Every excavation 

 will indeed present something worthy of notice to Ms view; but not contented 

 with observing merely these spots, where the labour of man has penetrated into 

 the interior of the earth, he must wander around the base of the lofty cliffs which 

 overhang the ocean, and observe the grand and instructive sections which nature 

 herself presents, and of which our own islands afford such numerous and admirable 

 examples. He must pursue the course of rivers into the interior, and observe the 



