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“ The Distribution of Ammonia/’ by Dr. R. Angus Smith, 
F.R.S., &c. 
If organic matter is everywhere ammonia is everywhere 
possible, and if that matter is decomposing, ammonia 
is everywhere. This is the general statement which 
this paper illustrates. It is now many years since 
it was observed by me that organic matter could be 
found on surfaces exposed to exhalations from human 
beings; but it is not till now that the full significance 
of the fact has shone on me, and the practical results that 
may be drawn from it in hygiene and meteorology. These 
results are the great extension of the idea that ammonia may 
be an index of decayed matter; the idea itself has been 
used partly and to a large extent, as illustrated in my 
“Air and Rain.” The facts now to be given enable us to 
claim for it a still more important place. The application 
seems to fit well the conditions already examined, and by 
this means currents from foul places have been readily 
found. This does not apply to the substances which may 
be called germs, whether it be possible to see them or not, 
because these are not bodies which have passed into the 
ammoniacal stage although some of them may be passing; 
those for example which are purely chemical and exert 
what we may call idiolytic action. This word, from 'Id tog, its 
own (peculiar), and Xvcrvg , decomposition, may serve to mark 
this peculiar action which was left by Liebig unnamed ; 
he used the vague term invented by Berzelius, namely 
catalytic. I have elsewhere recognised the two classes of 
germs, instead of any disputed one, without naming them. 
It is now many years since Liebig first surprised me by 
saying that iron ores and aluminous earths were capable of 
taking up ammonia, and if they were breathed upon 
we were able even to smell that substance. He, much 
about the same time, made numerous experiments in order 
to find the ammonia of the atmosphere, and to measure its 
