194 rNFLUEisrcE oir PRECiPiTATioisr. 



Tlie experience of observing persons confirms the common aay 

 ing, " All signs fail in dry times." This is partly an expression of 

 the law of prohdbilities^ according to which, the longer a particular 

 sjpell of weather has continued, the greater are the chances that it 

 will continue yet longer ; but there is a physical reason why, after 

 a long drought, appearances, which, under ordinary circumstances, 

 would almost certainly indicate an approaching rain-storm, prove 

 delusive. It is this : After a drought of some days, which gener- 

 ally occurs only after a protracted continuance of hot weather, the 

 surface of the ground is not only dry, but heated, and, hke any 

 other body of elevated temperature, throws off heat into the at- 

 mosphere. This heat tends to make the air capable of contain- 

 ing more humidity, and the vapor held in the atmosphere over an 



in relation to the frequency of this phenomenon, and was told by him that not 

 a drop of rain had fallen at that point for more than two years previous. 



The belief in the increase of rain in Egypt rests almost entirely on the ob- 

 servations of Marshal Marmont, and the evidence collected by him in 1836. 

 His conclusions have been disputed, if not confuted, by Jomard and others, 

 and are probably erroneous. See Foissac, Meteorologie, German translation, 

 pp. 634-639. 



It certainly sometimes rains briskly at Cairo, but evaporation is exceedingly 

 rapid in Egypt — as any one who ever saw a Fellah woman wash a napkin in 

 the Nile, and dry it by shaking it a few moments in the air, can testify ; and a 

 heap of grain, wet a few inches below the surface, would probably dry again 

 vsdthout injury. At any rate, the Egyptian Government often has vast quan- 

 tities of wheat stored at Boulak in uncovered yards through the winter, though 

 it must be admitted that the slovenliness and want of foresight in Oriental life, 

 public and private, are such that we can not infer the safety of any practice 

 followed in the East merely from its long continuance. 



Grain, however, may be long kept in the open air in climates much less dry 

 than that of Egypt, without injury except to the superficial layers ; for moist- 

 ure does not penetrate to a great depth in a heap of grain once well dried and 

 kept well aired. When Louis IX. was making his preparations for his cam- 

 paign in the East, he had large quantities of wine and grain purchased in the 

 Island of Cyprus, and stored up for two years to await his arrival. "When 

 we were come to Cyprus," says Joinville, Histoire de Saint Louis, §§ 72, 73, 



" we found there greate foison of the Kynge's purveyance The wheats 



and the barley they had piled up in greate heapes in the feeldes, and to looke 

 vpon, they were like vnto mountaynes ; for the raine, the whyche hadde 

 beaten vpon the wheate now a longe whyle, had made it to sproute on the 

 toppe, so that it seemed as greene grasse. And whanne they were mynded to 

 Carrie it to Egypte, they brake that swarde of greene herbe, and dyd flnde im- 

 der the same the wheate and the barley, as f reshe as yf menne hadde but nowa 

 thrashed it." 



