Remarks on Atmospheric Dust. 138 
he there suggests, and if I am wrong in dissenting from him, 
science can never suffer from a free and liberal investigation 
into its principles. Many of the facts stated in the article 
referred to, are doubtless true, but, as I apprehend, attribu- 
ted to wrong causes. I am not disposed to question that 
dusty molecules are visible on the highest mountains, and 
on the ocean, but I think all the phenomena may be ac- 
counted for by supposing that they arise from the roads, 
fields, woods, and other matter on the surface of the earth, 
disengaged by various causes. A brisk wind will raise it 
directly from the earth, and waft it to a great distance, it 
being so exceedingly subtle and tenurious as that the at- 
mosphere will support it even in a perfect calm. Perhaps 
in our climate there is not a day in the course of fifty years 
in which there is not a sufficient breeze sometime in the 
course of the twenty-four hours, to set in motion what we 
call atmospheric dust. And occasionally immense quan- 
tities are raised. In the stillest times, vegetables and 
trees are constantly depositing decayed matter, and some 
part of this, before it reaches the earth, doubtless floats 
away on the air. But this, says Mr. R. “is only a conse- 
quence of the first,” meaning that dust which it is the prop- 
erty of the air to deposit. Yet surely the clouds of dust, 
which are every where visible in a windy day, and that 
which is seen in a room when any extraordinary motion is 
produced, do not proceed from the atmosphere primarily. 
The only fact which he mentions, as tending in the least to 
invalidate the commonly received opinion on this subject, 
is, that dust is seen at sea. Now, whatever is supposed to 
be the origin of these molecules, certain it is that they are 
capable of floating a great while in the air, and of being car- 
ried to an immense distance. Is it absurd to suppose that 
the specific air which we once breathed sitting in our libra- 
ries, may now be floating 1500 miles off over the Atlantic ¢ 
If not, the dust with which it was charged here, may still 
accompany it there. Besides, the dust which is visible at 
sea, is visible only when the ship is nearly or quite becalm- 
ed; and may it not then arise in a great measure from the 
deck of the ship ? 
Mr. R. ‘calculates that on an average, from six to 
twelve inches are accumulated over the ground in one hun- 
dred years.” aking his lowest estimate, six inches for 
