190 VREDENBURG: SKETCH OF BALUCHISTAN DESERT. 



in a few hours, leaving a fine deposit of light-coloured mud, which 

 Plains of fine alluvium gradually accumulates, forming plains called 

 u pat." Some of these w pats/' where water is 

 available from a ka're'z, have.been locally cultivated, but as a rule they 

 constitute the most barren portions of the desert without any of the 

 bushes that occur at intervals in the stony plains, or even occasionally 

 take root amongst the sand dunes. 



These " pats," often half -concealed by the ever-encroaching 

 sand dunes, pass imperceptibly into the stony " dasht," and possess 

 Lake basins or usually very ill-defined limits. Where, however, 



they become of considerable size, and where 

 they are fed by streams that can give rise to more or less permanent 

 sheets of water, they exhibit a more distinct line of shore, and 

 gradually merge into the class of shallow lakes called "hamun." 

 The Lora Hamun, which is now absolutely dried up, is nothing more 

 than a gigantic "pat." The Hamun -i-Mashkhel, dry for the greatest 

 part, still contains water in two depressions, now separate, but 

 which some of the oldest inhabitants of the district remember having 

 seen once united. 1 The Gaud-i-Zirreh is described by Captain 

 McMahon as " a lake of salt brine fringed by an ever-encroaching 

 margin of solid salt." 8 



It may be mentioned here that these three lacustrine depressions 

 lie at very different altitudes. The Lora Hamun is at an altitude 

 considerably higher than the two others, and yet appears to be 

 perfectly independent from them. 8 Moreover, the drainage areas 



1 Information kindly communicated by Captain Roome. 



* Quart. Journ. Geol. Soc, Vol. 53, p. 2gi. 



8 The depression in which are collected the waters of the Helmand basin affords an 

 instructive illustration of the uncertain manner in which hydrographic basins are defined in 

 a desert region. The waters of the Helmand and of several rivers flow into two shallow 

 freshwater lakes surrounded by a reedy swamp. Sometimes the lakes overflow into this 

 marsh and thus become united. The fertile plain of Seistan proper is but the delta of the 

 Helmand, and has been formed partly by the sediments carried by that river into a lake 

 which formerly occupied the entire depression, and partly owing to the dessication of the 

 lake itself . The "hamuns" and marshes that still exist are separated in ordinary season 

 by a low watershed from the southern and lowest part of the depression, which contains the 

 Zirreh lake. Thus, in ordinary seasons the Gaud-i-Zirreh is the centre of a basin absolutely 



( I* ) 



