DR. R. ANGUS SMITH ON AMMONIA. 267 



in writing /(o) = I. Hence k=i—f{o)g. Substituting 

 this value in HerscheVs formula and expanding, we have 



ta-taf{o)gt+ ...,kc. 



Now, as g is very small, we may neglect terms beyond the 

 first two (unless t be very large) . Hence 



2«/(o)^^=I-T = A. 



If we assume the colour to be constant, A will be a con- 

 stant term. Now, let Q, denote the whole quantity of co- 

 louring-matter in the cylinder, and L the whole length of 



the column ; then g=j and the formula may be written 



2ff/'(o)-=^=A, or Q^=-r-^;j-^^ = constant. 

 L Sfl/(o) 



XXXIV. The Distribution of Ammonia. 

 By R. Angus Smith, F.R.S. &c. 



Kead April 30th, 1878. 



If organic matter is everywhere, the presence of ammonia 

 is everywhere possible ; and if that matter is decomposing, 

 ammonia is everywhere. That 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 



