FAEMERS' INSTITUTES. 



231 



substances, exposed to tlie sunshine absorbed more heat than light colored sub- 

 stances. The Swiss on the Alp? hasten the melting of the snow in spring-time 

 by sprinkling black substances on the snoAV, In Germany the vine-dressers 

 hasten the ripening of their grapes by covering the soil with black slate. 



The question arises, can we control the temperature of soils in our fields? It 

 is often said that the farmer is at the mercy of the weather, but unfortunately 

 the weather often has no mercy for the farmer. In 1868 I made a careful 

 investigation of the influence of muck on the temperature of soils. These 

 investigations extended from May 1st to Oct. 1st, embracing the period of active 

 vegetable growth. The observations were taken 3 times a day for the wliole 

 period, viz., at 7 A. M., and 3 and 9 P. M. The soils used for these experi- 

 ments were tile clay, clean sand, tile clay with 12 per cent of muck, and 

 sand with 12 per cent of muck. The temperature was determined by thermom- 

 eters buried 2 inches in the soil so as to find the temperature of the soil where 

 the roots work. In the folloAving table I give you the average temperature 

 for each month of each kind of soil xised in the investigation. The full results 

 of these investigations you will find in the Report of Board of Agriculture for 

 1808, pp. 137-149. 



It will thus be seen that the farmer has a certain control over the tempera- 

 ture of his soil by the use of muck. The gain of 1-} to 2^ degrees of tempera- 

 ture in the soil during the entire period of active growth is a great gain in our 

 cool climate. If any soil is deficient in vegetable mold, that deficiency should 

 be supplied from consideration of temperature, if for no other reason. 



Another proof of the increased temperature of dark colored soils is found in 

 the earlier ripening of certain crops. ''Girardin of France, found in a series 

 of experiments on the cultivation of potatoes, that the time of their ripening 

 varied 8 to 14 days, according to the color of the soil. He found on Aug. 25, 

 in a very dark humus soil, 26 varieties ripe ; in a sandy soil, twenty ; in clay, 

 19; in white lime soil only sixteen." — Jolnison's How Crops Feed, p. 190. 



This rule does not always hold good for grain crops, for you will often find 

 that wlieat will be more tardy in ripening on a very mucky soil. This may arise 

 from an excess of ammonia formed in such soils, which may retard the rijjening. 



II. Chemical Uses of Ifiiclc. 



1. Decaying vegetable matter is useful in agriculture because it powerfully 

 promotes decomposition of the mineral constituents of the soil. In all fertile 

 soils there is a large amount of mineral substances which have not been com- 

 pletely decomposed, which contain potash, soda, lime, magnesia, phosphoric 



