But let us look still further at the tropical currents. The true harmattan of north-western Africa (for the term is sometimes misapplied), hot and blistering, generated upon the sand of the desert--why does it blow from Sahara horizontally, on or over cooler surfaces, following the belt of rains as a N. E. trade? Why does it not ascend? The sirocco of north Sahara, the kamsin or chamsin of eastern Sahara, and the simoon of Arabia, which blow hot and suffocating from those deserts--why do they blow _from_ heated surfaces and _horizontally over_ cooler ones? Why do they not ascend? Arabia is surrounded on three sides by seas and gulfs, from which evaporation is rapid. Her interior deserts are extensive and intensely hot--why are they rainless? Why do they not have a _vortex_, a _monsoon_, or even a _shower_? Because there is no such law or action as this theory supposes. Those winds blow horizontally in obedience to other laws, and under the control of other and more powerful agents. But further still, what heating and ascending process is it that makes the variable winds north of the tropics? that brings in the warm air and fog of the Gulf Stream upon our _snow-clad coast_, in mid-winter, to increase the January thaw? Nay, what heating process is it that disturbs the calms of the polar regions with fresh breezes and gales, sometimes of the force of 6, when the _sun does not shine_, the thermometer is from 20 deg. to 40 deg. below zero, the _earth and sea one frozen surface_, and the hardy explorer dressed in furs, barely lives in his cabin covered by an embankment of snow, and heated by a stove? Gentlemen, meteorologists, it will not do. The theory is unsound; the assumed facts do not exist. The whole universe has not an agent, organic or inorganic, which can play such absurd and inconsistent pranks in the face of its Creator, as your various and complicated theories assign to caloric. Away with the theory and all its incidental and complicated and mystified hypotheses, they rest like a pall upon the science;--away with the whole system, and let us seek some agent whose _power_ and _adaptation_ correspond with the _extent_, and _simplicity_, and _magnificence_ of the phenomena, and, in some degree, with the _power_ and _wisdom of their Author_. CHAPTER V.