642 RUBBISH HEAPS. 
household refuse collected on the borders and within the limits 
of Cairo were so large, that the removal of them by Ibrahim 
Pacha has been looked upon as one of the great works of the 
age. 
These heaps formed almost a complete rampart around the 
city, and impeded both the circulation of the air and the com- 
munication between Cairo and its suburbs. At two points 
these accumulations are said to have risen to the incredible 
height of between six and seven hundred feet; and these two 
heaps covered two hundred and fifty acres.* During the occu- 
pation of Cairo by the French, the invaders constructed re- 
doubts on these hillocks which commanded the city. They 
were removed by Mehemet Ali, and the material was employed 
in raising the level of low grounds in the environs.*t 
In European and American cities, street sweepings and other 
town refuse are used as manure and spread over the neighbor- 
ing fields, the surface of which is perceptibly raised by them, 
by vegetable deposit, and by other effects of human industry, 
and in spite of all efforts to remove the waste, the level of the 
ground on which large towns stand is constantly elevated. The 
present streets of Rome are twenty feet, and in many places 
much more, above those of the ancient city. The Appian Way 
between Rome and Albano, when cleared out a few years ago, 
was found buried four or five feet deep, and the fields along 
the road were elevated nearly or quite as much, The floors of 
many churches in Italy, not more than six or seven centuries 
old, are now three or four feet below the adjacent streets, though 
it is proved by excavations that they were built as many feet 
above them.t 
* OLoT Bry, Egypte, i., p. 277. 
+ Egypt manufactures annually about 1,200,000 pounds of nitre, by lixivi- 
ating the ancient and modern rubbish-heaps around the towns. 
{ Rafinesque maintained many years ago that there was a continual deposi- 
tion of dust on the surface of the earth from the atmosphere, or from cosmical 
space, sufficient in quantity to explain no small part of the elevation referred 
to in the text. Observations during the eclipse of Dec. 22, 1870, led some 
astronomers to believe that the appearance of the corona was dependent upon 
