SUPPLEMENT TO THE 

 AND GARDENER'S JOURNAL. 



^ 



vol.. XVII. 3 



BOSTON, WEDNESDAY EVENING, OCTOBER 10, 1838. 



two. 14. 



AGRICULTURAL 



From tlie Genesee farmer. 

 CARBON IN PLANTS. 



At the late meeting of tlic British Association 

 It Liverpool, Dr Dalton communicated a paper 

 'on tlie Non.decomposition of carbonic acid gas by 

 3lant3." 



" He calculates that in 5000 years the animals 

 supposed to live upon the earth would produce but 

 X)l of carbonic gas, so tliat the assistance of plants 

 ,0 purify our atmosphere is not necessary. By ex- 

 periments he found that a hot house does not con- 

 .ain more or less carbonic acid by night or by day 

 Jian the e.xternal air, and the results were the same 

 irhen the e.xperiments were a number of times re- 

 )eated."* 



Dr Dalton is a great name in chemical philoso- 

 )hy, but we think the present system of vegetable 

 )hysiology is too well established to be shaken by 

 sxperiments so liable to fallacy as those menti.-'ned 

 ibove. To account for what is called the Aeration 

 if sap in plants, long exercised the skill and in^e- 

 luity of philoso;))<pro. The first step ti its solio'.' n 

 Tas made by Dr Priestly, the founder of pneutnatic 

 ;hemistry ; to Sennebier we are indebted for the 

 jbservation, that the presence of carbonic acid is 

 •equired for the disengagement of o.xygen gas du- 

 ring the day by the leaves of plants and that the 

 )xygen is derived from the decomposition of car- 

 jonic acid by plants has been fully established by 

 ;he researches of Woodhouse of Pennsylvania, 

 Saussure and Palmer. The most satisfactory de- 

 nonstration of this fact, however, was the following 

 sxperimeut by De Candolle : 



"Two glass jars were inverted over the same 

 water bath ; the one filled with carbonic acid gas, 

 he other with water, containing a thrifty sprig of 

 nint ; the jars communicating below by means of 

 the water bath, on the surface of which oil was 

 poured, so as to intercept all communication be- 

 tween the water and tlie atmosphere. The sprig 

 of mint was exposed to the light of the sun for 

 twelve days consecutively ; at the end of each day 

 the carbonic acid was seen to diminish in quantity, 

 the water rising in the jar to supply the place of 

 what was lost, and at the same time the plant ex- 

 haled a quantity of oxygen exactly equal to that of 

 the carbonic acid that had disappeared. A similar 

 sprig of mint, placed in a jar of the same size full 

 of distilled water, but without having access as 

 before to carbonic acid, gave out no oxygen, and 

 soon perished. In another experiment witli the 

 same apparatus as at first, o.xygen gas was substi- 

 tuted in tlie first jar instead of carbonic acid gas, 

 and no gas w^s disengaged in the jar, which con- 

 tained the sprig of mint It is evident, therefore, 

 that the oxygen gas obtained from the mint in (jc 

 first experiment, was derived from the decomp:isi- 

 tion, by the leaves of the mint, of the carbonic 



*Loadoa Alheneum, No. 519. 



acid, which the plant had absorbed from the wa- 

 ter."* 



This experiment, which has been repeated fre- 

 quently since and with every variation, is conclu- 

 sive as to the decomposition of carbonic gas, and 

 directly opposed to tlie conclusion of Dr Dalton. — 



Dr D. may be riglit as to tlie quantity of this 

 gas produced by animals, though it is evidently 

 ouly an approximation to tlie truth in such a case 

 can be made by calculation: but that plants do 

 decompose carbonic gas we think does not admit 

 of a doubt, and we further believe that in this way 

 most of the carbon appropriated by plants, and 

 which constitutes so large a portion of their struc- 

 ture is obtained in this way. When one considers 

 the structure of a hot house, the manner in which 

 it is supplied with external air, and the consequent 

 continual change of the atmosphere in such a build- 

 ing, it would have been more surprising had a dif- 

 ference existed between the internal and external 

 air, than that no such difference was discovered by 

 Dr Dalton. 



That the carbon obtained by the decomposition 

 of carbonic gas is retained by the plant is proved 

 by a beautiful series of experiments conducted by 

 Sau.'jure the younger, who found that this process 

 is attended with a sensible increase in the qaautity 

 of carbon, which the plant had previously contained. 

 He further discovered that it is in the green sub- 

 stances of the leaves alone that this process is 

 conducted ; a process which from its strong analo- 

 gy to a similar function in animals, may be con- 

 sidered as the respiration of vegetables. It takes 

 place only in the living plants, for if a leaf be 

 bruised so as to destroy its organization, and injure 

 its vitality, its substance is no longer capable of 

 decomposing carbonic acid under the influence of 

 the sun, or of absorbing oxygen in the dark. 



The respiration of man and animals appears to 

 be for the purpose of obtaining oxygen ; and this is 

 accomplished by the decomposition of the air in 

 the lungs, the oxygen being retained, while the 

 carbonic gas is rejected. In plants, however, the 

 food of which consists mostly of carbon, the object 

 of respiration appears to be, to retain the caibon 

 gained by decomposition, while the oxygen is 

 mostly rejected. It is clear therefore, that the 

 atmosphere is continually receivi.ig from the vege- 

 table kingdom a large accession of oxygen, and is 

 at the sauie time freed from an equal portion of 

 carbonic acid gas, both of which effects tend to its 

 purification, and its remaining adapted to the re- 

 spiration of animals. Nearly the whole of the car- 

 bon accumulated by vegetables, is so much taken 

 from the atmosphere, which is the primary source 

 from which they derive that essential aliment. 



The power of absorbing and retaining carbon 

 possessed by plants, depends on their vital power 

 or irritability ; hence the advantage of manures, of 

 lime, gyp.sum, &c. The quantity of these substan- 

 ces taken up by the plants themselves is small, but 



♦Roget's Bridgcwatcr Treatise, Animal and Vegetable 

 Physiolo^'. 



the quantity of carbon appropriated is rapidly in- 

 creased, and hence the vigorou» growth r>f the' 

 plant. This eflfect may be as clearly seen where' 

 gypsum is applied to clover, as perhaps in any other 

 case ; and here the growth is not because the gyp- 

 sum itself goes into the eircBlation and substance 

 of the plant in any considerable quantity, but be- 

 cause the p.iwer of appropriating carbon is in- 

 creased by the additional circulation or irritable- 

 energy of die plant When it is remembered that 

 carbon is the base of most nutritive substances, 

 and that this is in most cases, in the first place 

 drawn from tlie air by plants, the decomposition of 

 carbonic gas by vegetables cannot be viewed oth- 

 erwise than as a most wonderful proof of divine 

 wisdom and design in providing for the health and 

 nourishment of plants and animals. 



DEMONSTRABLE FACTS. 



V.'EIGHT OF CREAM AND HILK. 



In No. 24 of the Farmer, we published a com- 

 munication from "Truth " in which he thinks we 

 must have been mistaken in the experiment pub- 

 lished in a former paper, with regard to the spe- 

 cific giavity of cream and milk, and requested a 

 new e;.,.- haed should be made. We have not 

 had an opportunity to coiavily with his reqijcst i>i'- 

 til recently, but iiave now done it with a great deal 

 of care and accuracy. Our cow goes upon tlie 

 common, and usually we give her a few potato tops 

 or corn stalks, night and morning. She gives about 

 ten quarts of milk per day. The milk with which 

 the experiment was made, was milked at night and 

 strained into a tin pan. It was set in a cool situa- 

 tion and the cover but partially laid over it, in or- 

 der to let it cool. The next morning the cover 

 was placed entirely over it and in this condition it 

 set .37 hours. The cover was then removed and 

 tlie cream taken off as carefully as possible into a 

 glass tumbler. Then all remaining particles of 

 cream, which could not be so perfectly separated 

 from the milk, were taken off and a portion of the 

 milk put into another tumbler, and both were taken 

 to an accurate balance and weighed verj' carefully, 

 and a vial which will hold 1000 grains of distilled 

 water, when filled with the cream, weighed 978 

 grains and when filled with skimmed milk it 

 weished 1,03'2 grains. A portion of new milk from 

 the same cow was found to weigh 1,025 grains, 

 showing a difference of 54 grains in the specific 

 gravity of cream and skimmed milk, and a differ- 

 ence of 47 grains between cream and new milk. 

 Or that cream is 5 per cent, lighter than milk. 



This experiment was made with more accuracy 

 and care than the former, and shows a greater dif- 

 ference, which proves most conclusively the posi- 

 tion taken, that cream is lighter than milk. Altho' 

 there is a difference in the weight of milk from 

 different cows, and there will probably be a dlftor- 

 ence in the specific gravity of different parcels of 

 milk and cream ; but the principle we hold to and 

 have proved, is no new one. It has been estab- 

 lished by the best Chemists for years, and when 



