298 In the Upper Sierra 
manding point to link up the two places. Sometimes, on reaching 
a high point on some big cliffs, a compact little town with white- 
washed buildings surrounded by ruined walls has suddenly burst 
upon my view, nestled away in a secluded valley many hundreds 
of feet below, of whose existence I had hitherto only known by 
report. 
Judging from the number of these villages—in one district there 
are no fewer than sixteen within a seven-mile radius—there must 
have been a very large population here in the days of the Moors. 
Now, many of the villages are more than half in ruins and I know 
of at least one extensive village which is almost deserted, the chief 
inhabitants being a small detachment of Guardia Czvil and those 
few engaged in the cultivation immediately around. 
The rivers and streams of this region are most interesting to the 
geologist. The Guadiaro River which divides the famous Zao 
or cliff at Ronda has lower down in its course eaten its way 
through the limestone mountains in a marvellous manner. The 
most remarkable point is near Gaucin where it passes between two 
vertical cliffs only a few yards apart and 4oo ft. in height. So close 
do these great cliffs approach one another that here and there 
a big crag fallen from above is wedged in and forms a natural 
bridge. Here, the Guadiaro, after passing over a series of cataracts 
takes a final plunge into a dark abyss and emerges about a quarter 
of a mile lower down too ft. below the level of the entrance. 
Several friends of mine, during dry seasons when there is little 
water in the gorge, have endeavoured by swimming and wading 
to pass upwards through this mysterious natural tunnel but have 
been invariably baffled by a series of slippery water-worn weirs of 
natural rock in the gloomy caverns into which they have penetrated. 
Were I sound in wind and limb I should certainly try to pass 
through from above with plenty of rope to secure my retreat. 
The view of this gorge from the lower side is most magnificent. 
