224 Litter. . 







natc of ammonia and according to Dr Thomson 100 parts of urea 

 are composed of 39-5 parts oxygen, 82 5 azote, 14-7 carbon, 13-3 

 hydrogen. We see then, most satisfactorily, by the chemical analysis 

 of urea, that this substance contains all the elements of carbonate 

 of ammonia, which is the state, I apprehend, this salt exists in, so 

 largely, in the air of stables. 



Now and then, however, it is found in stables in a caustic state. 

 For, I have been frequently struck with a fact that takes place v.hen 

 lime-washers are employed in whitening the walls of stables, which 

 illustrates the phcenomenon called by Chemists single elective attrac- 

 tion, and proves at the same time the presence of this salt in im- 

 mense quantities. For, as the Volatile Alkali which is deposited 

 largely on the walls and ceiling of the stable, exists in the state of 

 carbonate, no sooner is the lime applied, than the carbonic acid 

 quits the ammonia, to unite itself to the lime, for which it has a 

 greater affinity, and, thus, at the same instant that the lime is con- 

 verted into chalk, and becomes mild, by the union of the carbonic 

 acid, the ammonia becomes caustic by the loss of it. 



The difference with respect to its pungency is instantly manif'^st. 

 For, I have always observed that the workmen (especially if they 

 were occupied in lime-washing filthy and ill-ventilated stables) 

 became unable to bear the effects of the caustic Volatile Alkai. U))oa 

 their organs of sight and smell, which, in these cases, proves so 

 insufferably pungent, as (o oblige them to desist from their work, 

 and run out into the open air, from time to time, in order to escape 

 from its influence. These facts may sei^e to forliiy others that have 

 been already adduced, by way of proving the great quantity of Vo- 

 latile Alkali which is mixed with the air of stabics, as it cr.iinoi be 



