MOST BENEFICIAL IN DRY SEASONS. 177 



drawn up around them. It is usual to put it in with 

 the sets ; but it was put around the young plants this 

 year, " only because," said Mr Geddes, " the drought 

 was such that I saw if something was not done I should 

 have no crop at all." An English farmer would hardly 

 believe he had done anything towards saving a crop of 

 potatoes if he had only sprinkled a bushel of gypsum over 

 an acre of the land in which his potatoes were growing. 



This beneficial action of gypsum, notwithstanding 

 all that has been written upon the subject, is still very 

 wonderful, and not the less so that in so many places, 

 and in so many circumstances, it fails to produce any 

 sensible effect. Mr Ruffin, states that in the Carolinas 

 it is found to produce the best effects upon land which 

 has been already limed ; and here, where its beneficial 

 influence is so manifest, the land is naturally rich in 

 lime. I have caused an analysis of a portion of the 

 green shale from which the soil on Mr Geddes's farm is 

 formed to be subsequently made, and have found it to 

 contain as much as 23 per cent of carbonate of lime, 

 and 13 per cent of carbonate of magnesia.* It may be, 

 therefore, that while this marly and magnesian charac- 

 ter of its soil certainly makes the district more favour- 

 able to the growth of wheat, that it has some influence 

 also in disposing it to be beneficially acted upon by 

 gypsum. This substance does not appear to require 

 rain to aid its effects, since it is applied especially in 



* The composition of this slaty rock from Mr Geddes's fai'm at 

 Fairmount, near Syracuse, was as follows : — 



Water of combination, . . . 3.02 



Alumina, ..... 9.85 



Oxide of iron, .... 2.87 



Carbonate of lime, .... 23.22 



Carbonate of magnesia, . . . 13.81 



Carbonate of iron, . . . 1.45 



Insoluble siliceous matter or silicates, . 46.13 



100.35 

 The presence of phosphoi'ic acid in this sample was not appreciable. 

 VOL. I. M 



