Hyland — On some Specimens from Wad ij- Haifa. 447 



the same writer, the heat of the sun, causing the unequal expan- 

 sion of the minerals which build up the rocks, the force of the 

 wind producing constant attrition of the disjoined particles, and 

 torrential rains. A very striking confirmation of this conclusion 

 is afforded by a study of the composition of the Nile waters. In 

 spite of the enormous evaporation and constant concentration the 

 waters of the Nile must undergo during its passage of 1400 miles 

 through regions of exceptional heat and drought, it is shown that 

 these waters actually contain far less dissolved matter than the 

 Thames, the Lea, the Severn, or the Shannon. 1 The chemical 

 disintegration of rocks being so largely due to the action of rain 

 and vegetation, it is not surprising to find that, where these kinds 

 of action are almost entirely absent, but little evidence of chemical 

 change is exhibited by their mineral-constituents. It is therefore 

 to be expected that the waters which traverse such regions will be 

 characterised by a deficiency in the proportion of solids in solution, 

 and by anomalies in the degrees of temporary and permanent 

 hardness. As a matter of fact, the waters of the Nile really hold 

 in solution little more than one-half the per-centage of mineral 

 matter which is present in the river waters of temperate and rainy 

 regions. 



1 C. M. Tidy, Eiver "Water. Journal of the Chemicd Society, 1880, vol. xxxvii. 

 pp. 268-327. 



