THE SOUTHERN PLANTER. 



273 



observe that the lime water, which at first 

 was transparent, is now white like milk, 

 [Experiment performed. Mr. Nesbit then 

 showed by similar experiments that car- 

 bonic acid was given off by burning wood, 

 paper, wax, and other similar bodies con- 

 taining carbon.] I may here observe that 

 we ourselvos, and other animals, are all 

 like so many steam-engines. We are ob- 

 liged to take in so much food every day 

 to maintain the animal heat, and to keep 

 the machine in motion; by every inspira- 

 tion we take in oxygen, and by every ex- 

 piration we give out carbonic acid, which 

 is derived from the combustion of the char- 

 coal of the food which we have eaten. If I 

 pass the breath from my lungs into this lime 

 water, you will find the same kind of de- 

 posit that you have before observed produc- 

 ed from the gas proceeding from the burn- 

 ing of charcoal. [Experiment performed.] 

 So that you see, gentlemen, whatever may 

 be the manner in which charcoal or carbon 

 is burnt whether it be burnt in the form of 

 charcoal itself, or as it exists in paper, or 

 wax, or tallow, or as food in the animal 

 system, the result of the combustion is 

 carbonic acid gas. Now, in order that 

 the properties of this substance may be 

 well impressed upon your minds, I shall 

 place it before you in tolerably large quan- 

 tities, and will endeavour to show you 

 some of its properties. I have here a 

 quantity of chalk, which is carbonate of 

 lime — that is to say, a combination of lime 

 with carbonic acid. I dare say many of 

 you have heard of poor unfortunate peo- 

 ple sleeping near lime kilns, and being 

 killed by the fumes which came from them. 

 Those fumes consisted of carbonic acid. 

 Now, I can liberate the carbonic acid in 

 an easier way from the carbonate of lime 

 than by heating it ; all I have to do for 

 that purpose being to put a stronger acid 

 to the carbonate, when the strong acid 

 will take the lime, and the carbonic acid 

 will escape. The acid I shall use is call- 

 ed muriatic or hydrochloric acid, or spirits 

 of salt, and I shall now put it over the chalk 

 in this jar. [Experiment performed.] — 

 You here see a very considerable efferves- 

 cence, which is caused by the liberation 

 of the carbonic acid. Now, carbonic 

 acid, gentlemen, is one and a-half times 

 heavier than common air, and that is the 

 reason why it collects at the bottom of 

 wells and pits, and other places of the 



18 



same kind. We have it now collecting 

 in this vessel [pointing to the large glass 

 jar;] though we cannot see it, it is cer- 

 tainly there. I speak of carbonic acid ; I 

 speak of what is contained in the appa- 

 rently-empty space above the liquid in the 

 jar, I will send down into the jar what I 

 may call a little searcher [referring to a 

 little ignited wax taper at the end of a 

 wire ;] and as soon as this searcher comes 

 in contact with the carbonic acid gas in 

 the jar (which may represent a well con- 

 taining this gas), the light will go out. — 

 [The flame was here let down into the 

 jar, and was instantly extinguished.] If a 

 man were to go down into a well of the 

 same kind, his life must go out just as that 

 flame went out; for what prevents the 

 combustion of a candle would prevent 

 combustion in a man ; the man's life 

 would be as utterly extinguished as was 

 that flame. But I have to show you also 

 that this gas is identical with that which I 

 have previously produced by the burning 

 of charcoal. [Some of the gas was here 

 poured into a vessel containing lime wa- 

 ter, and the white precipitate of carbonate 

 of lime was immediately produced.] — 

 Now, gentlemen, I have been the more 

 more particular with these experiments 

 upon carbonic acid because, although the 

 thing is invisible to your eyes, it is never- 

 theless quite capable of proof that it is 

 from this gas that every one of your vege- 

 tables derives the whole of the charcoal 

 which they contain. I have just one more 

 experiment to make before I proceed. If 

 I take this glass, containing carbonic acid, 

 and pour the gaseous contents over one 

 of these candles, I have not the slightest 

 doubt that the candle will go out. [Ex- 

 periment performed, the result being what 

 was intimated it would be.] ] must now 

 endeavor to give a practical turn to the 

 subject matter of the lecture. I have en- 

 deavoured to point out the nature of the 

 soil and the effect of drainage upon it, 

 and the necessity of keeping it in a pul- 

 verised form, in order that ""it may be in a 

 proper slate to absorb moisture, and to 

 appropriate the various substances con- 

 tained in the atmosphere. J have also de- 

 scribed the four substances which consti- 

 tute the organic matter of plants — the ox- 

 ygen, which burns; the hydrogen, which 

 is burnt; the nitrogen, which is found in 

 saltpetre and nitrate of soda, and the 



