80 BOARD OF AGRICULTURE. 



under the influence of carbonic acid. The object of this 

 experiment was to bring gypsum and magnesia compounds 

 under common influences in the soil ; for every agricultural 

 soil contains organic matter, which, by gradual decompo- 

 sition, becomes a constant source of carbonic acid. In 

 testing the washings of this mixture, some time afterwards, 

 I found that in the solution was sulphate of magnesium : 

 in other words, the sulphuric acid of the gypsum had passed 

 under the influence of the carbonic acid of the magnesium, 

 and formed sulphate of magnesia (common Epsom-salt), 

 while the lime combined with the carbonic acid, and formed 

 common carbonate of lime, which was mixed up with the 

 soil in an insoluble form. 



The second experiment was carried out in the following 

 way : Sulphate of lime, carbonate of magnesia, and common 

 salt (sodium chloride) were mixed, and placed under the 

 influence of carbonic acid, to learn whether common salt 

 suffered any transformation which might aid in the expla- 

 nation of a good many of the good results, as well as the 

 failures, from the application of common salt as a fertilizer ; 

 and a critical examination of the washings proved that the 

 chlorine of the sodium had passed over to the magnesium, 

 and formed chloride of magnesium, a compound well knowA 

 as injurious to plant-growth ; the sulphuric acid of the gyp- 

 sum had passed over to the sodium, and formed common 

 sulphate of soda, or Glauber' s-salt ; and the lime was left as 

 carbonate of lime. Therefore, before you draw a conclusion 

 from a single experiment, repeat the experiment. 



Mr. Flint. Dr. Nichols, in speaking of top-dressing with 

 barnyard manures or compost, advised that they should be 

 put on in the fall, not too early, and not at a time when 

 they would produce late growth. Possibly I have not very 

 clearly stated his point ; but I think he overlooked, no doubt 

 quite inadvertently, the fact that a growth, no matter what 

 time in the fall it takes place, is a growth which is a perma- 

 nent advantage to the plant itself. It must be borne in 

 mind that the root-power of a plant is very much in propor- 

 tion to the surface or the leaf-power. If the leaf is small, 

 the root will be small; that is, you will get but a small 

 plant-root in which to store up the rich materials for the 

 use of the plant early in the spring. Now, any thing, it 



