286 CALCAREOUS MANURES— APPENDIX. 



But to this very general operation of animal life, there is as general and 

 as operative a countervailing action in vegetable life. Carbonic acid gas 

 is essential to the health and growth of plants, and serves to furnish them 

 with a very large if not indeed their larger proportion of bulk and sub- 

 stance. All that part of every vegetable substance which can be converted 

 to charcoal (or carbon) has been furnished to the plant from the atmo- 

 sphere in the shape of carbonic acid gas, which is a combination of oxygen 

 gas and carbon. The leaves of growing plants absorb this ingredient 

 from the atmosphere, and retain and fix the carbon as part of their sub- 

 stance, and evolve the pure oxygen ; thus taking from the air some of its 

 poisonous ingredient, and adding to it new supplies of the purifying or 

 health-supporting gas.* 



It follows necessarily from these premises that if by any means these 

 universal powers and continual action of plants, to absorb carbonic acid 

 gas and evolve oxygen gas, be in any manner increased, that proportional 

 increase must be given by the first to the growth of the plant, and by the 

 second, proportional purification and healthiness to the atmosphere. 



To these general views and positions the recent observations of Dr. 

 Wight apply admirably. He ascertained, by a series of careful and well 

 conducted and repeated experiments, that the diffusion of carbonate of lime 

 in water with which plants were nourished, caused in the plants a great 

 and remarkable increase of both the above named actions ; so that they 

 absorbed much more, in some cases a quadrupled quantity, of carbonic 

 acid, and evolved as large an increased quantity of oxygen gas. If this be 

 so— and the manner of the experiments stated leaves no ground to doubt 

 the accuracy of their conduct, or of their results— then there can be no 

 question of the following important deductions : that besides all other modes 

 and powers of fertilizing action of lime in soil, as maintained in this essay, 

 it also causes plants to draw from the atmosphere a very large accession 

 of nutriment; and to increase in proportion the measure of their ordinary 

 purification of the atmosphere. And therefore, these interesting and new ob- 

 servations serve to confirm and to show additional and important reasons 

 for tlie operation of calcareous manures both for increasing the productive- 

 ness of lands, and of lessening the amount of disease among the residents 

 thereon and in the vicinity. 



NOTE VIII. — Extension of subject from page 161. 



DIKECTIONS FOR BURNING AND APPLYING OYSTER-SHELL LIME. 



The following directions and remarks may be useful to some of those 

 persons to whom shell-lime will be cheaper than either marl or stone lime. 



Oyster-shells are brought by vessels to the landing places of the purchasers 

 on the James river, and sold on board usually at 62^ cents the hogs- 

 head, of 18 heaped bushels. Where fuel is plenty, the shells and dry pine 

 wood, in alternate layers, are built up in a heap of cubical form for burning. 

 In this manner, if judiciously executed, 12 cords of wood are sufficient to 

 burn 100 hogsheads of shells to quick-lime. A more careful mode of burn- 

 ing was used by the late Fielding Lewis, of Weyanoke, which was de- 

 scribed in an account of his farming in the Farmers' Register, for June, 1833, 

 and which will be copied below, together with his mode of application ; 



• As this is the greatly preponderating action of vegetables, the smaller reverse opera- 

 tion (which takes place at night) is passed over, as unnecessary to be referred to more 

 fully than in this manner. 



