240 Intelligence and Miscellaneous Articles. 



apparent velocity because they pass over regions moving more 

 rapidly than themselves, but they undergo a further retardation and 

 from a different cause: in expanding they are raised, they recede 

 from the centre of the globe, and assume a greater radius ; and this 

 must evidently retard their angular velocity as the actual speed with 

 which they moved is transferred from a less to a greater circum- 

 ference. The expansion of the waters as they approach the equator 

 thus causes an increase of rapidity in the equatorial current, which, 

 as was said above, is caused by the slower relative speed of the 

 water as compared with that of the earth. If the temperature of the 

 waters flowingtowards the poles remained constant, they would restore 

 to the globe the stored-up energy acquired from the impulsion of the 

 equatorial coasts ; but as they approach the poles their temperature 

 gradually falls and they shrink in bulk. This gives rise to a pheno- 

 menon contrary to that which happens in the currents flowing 

 towards the equator : the water in shrinking approaches to the 

 centre of the globe, it therefore transfers its actual velocity from a 

 larger to a smaller circumference, and consequently its motion is 

 increased relatively to that of the earth. Hence the waters flowing 

 towards the poles tend to impart to the globe more mechanical work 

 than they abstracted from it at the equator, and consequently 

 to impel it forwards more than they retarded it. The heating 

 of the equatorial regions thus tends to render the currents more 

 rapid, and, as a consequence, to increase the earth's diurnal motion ; 

 and might be a means of compensating, in the manner described, the 

 losses from friction &c, and of maintaining the motion of the waters 

 and of the globe, which, as we have shown, would be gradually dissi- 

 pated without a continual influx of mechanical work from without. 



The source of such mechanical work, tending to maintain the mo- 

 tion of the waters and of the globe, is evidently the solar heat ; but 

 in what manner does it produce the dynamical effect ? 



The water is expanded by the solar heat; in the act of expanding 

 it recedes from the earth's centre, that is to say, it is raised ; and 

 this operation requires an equivalent expenditure of work, as it im- 

 plies the lifting of a weight. The solar heat not only heats the 

 waters, but at the same time it imparts to them a certain quantity of 

 potential energy in consequence of having lifted them. A portion 

 of the solar heat is thus transformed into potential energy, which, as 

 the waters cool and shrink in flowing towards the poles, takes the form 

 of motion and communicates a greater velocity to the current, tending 

 to compensate the loss of motion and of power which the currents 

 and the globe are continually undergoing from the effects of friction. 



According to this idea a portion of the solar heat received by the 

 equatorial regions of the globe is converted into potential energy, in 

 expanding and consequently raising the waters flowing from the 

 poles towards the equator ; and this potential energy, assuming the 

 active form in the shrinking and consequent lowering of the waters 

 as they flow towards the poles, tends to restore to the currents the 

 motion lost through friction, and may be a means of supplying mo- 

 tion to the globe, or of maintaining its velocity of rotation. 



Palermo, February 14, 1870. 



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