Mr. H. F. Talbot on the Iodide of Mercury. 297 
There is no doubt from this that the ammonia observed in 
the rust of iron was obtained from the atmosphere. 
Herman*, in an essay ‘On the decay of wood,” mentions an 
experiment in which the nitrogen of theatmosphere was directly 
absorbed and partially converted into ammonia by the decay 
of fresh wood. Herman found nearly one-third part of the 
nitrogen, which according to his experiments existed as a con- 
stituent of the wood, in the products of its decay. He con- 
cludes from this that two parts escaped in the form of ammonia. 
The most perfect process of decay with which we are ac- 
quainted is the production of acetic acid from alcohol. If 
the nitrogen of the atmosphere possessed the property of 
taking part in these metamorphoses instead of pure acetic 
acid, an ammoniacal salt of it would be obtained in the quick 
process for the manufacture of vinegar, where the woody fibre 
undergoes a slow decay with the alcohol. As yet however no 
ammonia-formation has been observed. 
The process of decay of organic substances which contain 
little or no nitrogen at the surface of our planet, is as old as 
the occurrence of living matter upon it; it is so general and 
everywhere perceptible that our atmosphere would soon be 
poisoned with ammonia, there being no such chemical attrac- 
tions for nztrogen gas (as an element) as for oxygen, and its 
amount of nitrogen would certainly have decreased, if this most 
indifferent of all gaseous elements possessed the property of 
contributing as such to the formation of ammonia. 
LILI. On the Iodide of Mercury. By H. F. Tarzor, Esq., 
F.RS., Sc. 
To the Editor of the Philosophical Magazine. 
Dear Sir, 
GIVE me leave to reply in a few words to some remarks 
inserted in the last Number of your Journal. I will not 
occupy much of your space in so doing, for this appears to 
me to be really a very simple case. It is a mere question of 
dates, and nothing else. 
finding a paper inserted in your Journal, describing che- 
mical and optical phenomena which appeared to be almost ex- 
actly the same with what I had published six years previously, 
I took the liberty of calling your attention toit. At the same 
time I carefully discriminated, as being ‘a fact both new and 
important,” the phenomenon described in the latter part of 
the paper, since it was different from anything which I had 
observed. I am ata loss to know why objection should be 
taken to such a communication as this. It was simply a claim 
* Journ. fir Prakt, Chemie, Bd, xxvii. S. 165, 
