426 



Miscellaneous, 



Now, these three compounds — carbonic acid, water, and ammonia 

 — form the food of plants. They all exist in the air, from whence 

 they are extracted by the vegetation which covers the earth. The 

 grand difference between animal and vegetable life is, that this carbonic 

 acid, which is fatal to animals, is the primary food of plants; and 

 that whilst plants are continually inspiring this noxious gas, animals 

 are as constantly expiring it. There are certain constituents in the 

 food of man and animals, which are not at all calculated to assist in 

 the nourishment of the body, but which are, nevertheless, indispen- 

 sable in supporting the process of respiration. Such are starch, sugar, 

 and gum. I had the honour, on a former occasion, of explaining this to 

 you in detail. These substances, in supporting respiration, are con- 

 verted into carbonic acid and water. Hence it is that animals continu- 

 ally expire this gas. But there are other substances also exclusively 

 adapted for the nutrition of the system, and which, when present in 

 superabundance, are separated as excrementitious matter. In such 

 substances nitrogen abounds. Hence during their decay, ammonia is 

 generated. When animals die, their bodies enter into a state of pu- 

 trefaction, or, to speak more correctly, the constituents of which their 

 bodies are composed, change their form, and are converted into carbo- 

 nic acid and ammonia. 



Conceive the thousand millions of men who inhabit the globe, 

 and the myriads of animals which teem on its surface — all sending 

 into the air, every day, vast quantities of that noxious gas. Con- 

 ceive the vast amount of fuel constantly generating the same com- 

 pound, and it is obvious that the earth would soon become uninha- 

 bitable were there no means of removing it from the atmosphere. 

 Nor is this all. As carbonic acid is fatal to animal life, in as great 

 a degree is the oxygen of the air necessary for its support. But 

 this oxygen is always withdrawn from the air as carbonic acid is 

 formed ; for carbonic acid consists of carbon and oxygen. Thus, in 

 burning, ten cwt. cf coal consumes 32,000 cubic feet of oxygen gas ; 

 so that this town of Manchester (calculating its inhabitants at 

 300,000, the round number of the former census) consumes, for 

 domestic purposes alone, exclusive of the manufactories, no less than 

 23,014,285,714* cubic feet of oxygen, and sends into the air a like 

 quantity of pestiferous carbonic acid in its stead. Again, each man 



* The calculation is as follows :— It has been found that a small town of 7000 inhabitants 



consumes in fuel, for domestic purposes, 551 million cubic feet of ox3'gen. 



551,000,000+ 3000,000 



=-23,614 285,714 



