1044 
THE NATIONAL GEOGRAPHIC MAGAZINE 
Photo from “The Gateway to the Sahara,” by Chas. Wellington Furlong: Scribner’s 
SUDANESE BLACKS ANNOUNCING A RELIGIOUS DANCE 
when Rome’s power began to weaken. 
The wild tribes of the desert, which had 
been kept down by force, took advantage 
of Rome’s weakness and attacked the 
boundaries of the colony. ‘The elaborate 
system of irrigation could only work 
when there was absolute security. When 
peace was no longer assured, the agricul- 
turist was hindered in his work. 
A second cause of the decline of the 
country—which is, however, still a point 
of controversy—is a change in the cli- 
matic conditions of the region. There is 
probably some truth in this assertion. 
Every man who has seen, in the midst 
of the desert, the ruins of Roman castles 
and villas comes to the belief that some 
mightier power is responsible for such 
a change. 
A great tragedy has been enacted here. 
Mr. Hanns Vischer gives us a descrip- 
tion of what he saw-in Gherria, the ruin 
of a Roman town on the road between 
Tripoli and Fezzan. . “It was a pitiful 
sight to behold a hungry-looking crowd 
of fanatics under the ruins of the Roman 
gateway bearing the: inscription, “Pro. 
Afr. Ill.” (Provincia: Africa Illustris).” 
Mr. Pervinquiére, the French geolo- 
gist, who traveled from Tripoli to Gha- 
dames in the spring of this year, says of 
the country which he. traversed: “It is 
difficult to form an idea of the desola- 
tion of the immense solitudes. For days. 
and days we advanced over naked rock. 
No trace of vegetation. Everything is 
cleared away by the wind, which rules 
over these plateaus. . . ‘The reason 
for such a sterility has not to be sought 
in the geological constitution, but in the 
