THEORY OF THE NON-ACTION OF GYPSUM. 151 



would increase or restore the capacity of the soil to receive benefit 

 from gypsum. 1842.] 



1832. The following are my views of the general causes of the 

 inertness and worthlessness of gypsum as manure, on all acid soils, 

 and for the different and valuable results from gypsum, after the 

 soils have been made calcareous. 



I do not pretend to explain the mode of operation by which 

 gypsum produces its almost magical benefits ; it would be equally 

 hopeless and ridiculous for one having so little knowledge of the 

 successful practice to attempt an explanation, in which so many 

 good chemists and agriculturists, both scientific and practical, have 

 completely failed. There is no operation of nature heretofore less 

 understood, or of which the cause, or agent, seems so totally dispro- 

 portioned to the effect, as the enormous increase of vegetable 

 growth from a very small quantity of gypsum, in circumstances 

 favourable to its action. All other known manures, whatever may 

 be the nature of their action, require to be applied in quantities very 

 far exceeding any bulk of crop expected from their use. But one 

 bushel of gypsum spread over an acre of land fit for its action, may 

 add more than twenty times its own weight to a single crop 

 of clover hay. 



But without pretending to account for the wonderful action of 

 gypsum as manure, and without entertaining any confidence in any 

 of the numerous theories heretofore presented, [not excepting the 

 latest set forth, by Professor Liebig], I concur in the general' 

 opinion expressed by Davy. This accurate investigator, who took 

 nothing upon trust which could be subjected to the test of rigid 

 experiment, pursued that mode to obtain light on this obscure sub- 

 ject. He found by chemical analysis, that gypsum was always 

 present in the ashes of red clover, and ia quantity, in a good crop, 

 amounting to three or four bushels to the acre. He inferred that 

 gypsum, thus always forming a portion of the clover plant, was 

 essential to its healthy existence ; and that it is necessary to the 

 structure of the woody fibre of clover and other grasses. But it is 

 enough if Davy was correct in the main opinion, that a certain 

 though very small proportion of gypsum is an essential component 

 part of certain plants, of which the clover tribe furnishes the most 

 noted examples. If this be so, no matter what may be the office 

 or function of the gypsum, the small amount necessary for the de- 

 mands of the plants must be present in the soil, or otherwise the 

 plants needing it cannot live, or maintain a healthy growth. It will 

 follow, further, that on soils well adapted for clover in other 

 respects, but almost totally deficient in gypsum, the application 

 of so small a dressing as one bushel of that substance to the acre 

 may enable a full crop of clover to grow, and twice or thrice as 

 much as the land could have brought without this small application. 



