400 Rafinesque on Atmospheric Dust. 
- It does not appear that it has any bad influence on men and 
- animals breathing it along with air, unless it should be accu- 
mulated in avery intense degree. 
13. At Segesta, in Sicily, are to be seen the ruins of an 
ancient temple; the steps, which surround it on all sides be- 
low the pillars, are built on a rock, on the top of a hill 
detached from any other higher ground. Yet now all the 
steps and the base of the pillars are under the ground, which 
has accumulated from this dust and the decay of plants (not 
trees) to which it has afforded food. There are from five to 
eight feet from the rock to the surface of this new soil, which 
has chemically combined in a variety of degrees of hardness. 
This soil has arisen there in about 2000 years, notwithstanding 
the washings of rain. I quote this as a remarkable instance of 
the increase of soil by aerial deposits, among many which 
have fallen under my personal examination. 
14, It is commonly believed that the dust of our rooms is 
produced by the fragments of decomposed vestments, bed- 
ding, furniture, &c.; this cause increases it, and produces a 
different dust, which mixes with the atmospheric dust; but it 
is very far from producing it. 
15. The dust of the open air is ascribed to that raised from 
roads and fields, by the pulverization of their surface; but 
this secondary and visible dust is only a consequence of the 
rst. From whence could arise the dust observed by the 
means of the sunbeams in a dark corner, in winter, when the 
ground is frozen, or when it is wet and muddy, or at sea, OF 
on the top of rocky mountains? 
16. It is therefore a matter of fact, worth taking into con- 
sideration by geologists, that the air stil] deposits a quantity 
of dust, which must have been much greater in. former pe- 
riods; just as the sea deposits still a quantity of earthy and 
saline particles dissolved in it, and. which were. formed on 
its bottom. Water being more compact, deposits rocks. Ait, 
which is less dense, deposits a pulverulent matter! 
