266 The American Naturalist. [March,. 
D. Louis Carranza, a physician and a close observer, the secretary of 
the philologist, G. P. Zegarra. 
Among well-known geographers who have passed away during 1892 
may be mentioned Bates, the “ Naturalist on the Amazon”; Grant, 
Speke’s companion to the sources of the Nile; Lord Arthur Russel), 
Professor Moseley, and Sir Lewis Pelly, who, while stationed at 
Bushire, adventurously penetrated in British uniform to the stronghold 
of the fanatical Wahabis. This was in 1865. At Riyadh he met the 
- blind Saiyid Amir, and was allowed, in appearance, to depart in safety, 
but on their homeward march the party found that their water-bottles 
had been poisoned, and suffered agonies of thirst, the only refreshment 
they could gain being to pour the water over their wrists. 
In an address delivered before the Berlin Geographical Society, 
Professor J. Walther compares the desert regions of America with 
those of Africa, and finds the similarity greater than is generally sup- 
posed. Both are characterized by four distinct types of denudation, 
gravel beds, sand-dunes, loam regions and salt deposits. In both the 
mountains rise out of the plains like so many islands, without any inter- 
vening debris, and in both the “amphitheatre ” formation is common. 
Both exhibit the denudating powers of heat and dryness, the first split- 
ting the rocks into fragments, while the dry winds whirl the dust 
into heaps. No doubt water, even here, is the chief agent, but it has 
not more than sixty days in which to accomplish its work. The chief 
difference between the American arid lands and those of North Africa 
is the steppe vegetation of the former. 
