66 
But as people don’t read much on a subject, I will begin 
at the end. I have been for two years attempting to 
measure the amount of putrescible matter in the air ol 
the towns and country places, and I have succeeded to a 
considerable extent. I also measure the amount that has 
putrefied and left its remains in the air— -the sewage of the 
atmosphere. Some of my results are published; I have 
promised some very soon, and some have been ready for 
printing, under the head of Chemical Climatology. The 
proof of organic matter is old. I seek the quantity in 
various towns and parts of towns. 
I shall not here give a history of the enquiries. So many 
people claim to have something to say in the matter, that I 
might amuse myself, if not the public, by a long account. 
At present I profess to keep almost entirely to my own 
work. The knowledge of organic matter in the air has 
never been absent entirely from men’s minds in historic 
times ; but the words of Bishop Berkeley are so clear that I 
prefer to quote them. Besides he is far enough back for 
the purpose. He says in Siris (par. 140) : — 
“Nothing ferments, vegetates, or putrefies without air, 
which operates with all the virtues of the bodies included 
in it, that is, of all nature. * * * The air, therefore, is 
an active mass of numberless different principles, the general 
sources of corruption and generation; on the one hand, 
dividing, abrading, and carrying off the particles of bodies, 
that is, corrupting or dissolving them ; on the other, pro- 
ducing new ones into being, destroying and bestowing 
forms without intermission.” 
And in paragraph 141 he says : — 
“ The seeds of things seem to be latent in the air, ready 
to pair, and produce their kind whenever they light on a 
proper matrix. The extremely small seeds of ferns, mosses, 
mushrooms, and some other plants, are concealed and wafted 
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