THE SOUTHERN PLANTER. 



683 



times to cool down through 

 her of deo^rees. In the 



of temperature. The condensed water 

 collects in drops — it is dew; or in the 



colder seasons it crystalizes as hoar frost. 1 are given his results 



The special nature of the surface of thelsumed as 100. 

 soil is closely connected with the mainte- ^" 



following 



lime sand 



ven num- 

 table 

 beins: as- 



is 



nance of a uniform temperature, with the 

 prevention of too great heat by day and 

 cold by night, ami with the watering of 

 vegetation by means of dew. It is, how- 

 ever, in many cases only for a little space 

 after seed time, that the soil is greatly con- 

 cerned in these processes. So soon as it 

 becomes covered with vegetation, the cha- 

 racter of the latter determines to a certain 

 degree the nature of the atmospheric 

 changes. In case of many crops, the soil 

 is but partially covered, and its peculiari- 

 ties are then of direct influence on the 

 vegetation it bears. Among these quali- 

 ties the following remain to be noticd^d : 



1. The color of the soil. — It is usually 

 stated that black or dark colored soils are 

 sooner warmed by the sun's rays than 

 those of lighter color, and remain constant- 

 ly of a higher temperature so long as the 

 sun acts on them. An elevation of seve- 

 ral degrees in the temperature of a light 

 colored soil, may be caused by strewing 

 its surface with peat, charcoal powder or 

 vegetable mold. To this influence may 

 be partly ascribed the following facts. — 

 Lampadius was able to ripen melons even 

 in the coolest summers, in Friberg, Saxo- 

 ny, by strewing a coating of coal dust an 

 inch deep over the surface of the soil. In 

 Belgium and on the Rhine, it is found that 

 the grape matures best when the soil is 

 covered with fragments of black clay slate. 

 Girardin found in a series of experiments 

 on the cultivation of potatoes, that the 

 time of their ripening varied eight to four- 

 teen days, according to the color of the 

 soil. He found on August 25th, in a very 

 dark humus soil, twenty-six varieties ripe; 

 in sandy soil twenty; in clay nineteen; 

 and in white lime soil, only sixteen. It is 

 not difficult to assign other causes that will 

 account in part for the results here men- 

 tioned ; there seem to be no accurate and 

 extensive observations on this point. That 

 dark soils may actually attain an increas- 

 ed temperature of three to eight degrees 

 over light colored soils, is a matter of di- 

 rect observation. 



2. RapidUy with which the soil cools and 

 wq,rms, — Schiibler found that different soils 

 heated to the same point required different 



Lime sand, . . 100. 



Slate marl, . .98.1 

 Quartz Sand, . . 95.6 



Potter's clay, . . 76.9 



Gypsum, . . 73.8 



Clay loam, . . 71.8 



Plough clay land, , 70.1 



Heavy clay, . . 68.4 



l\]re gray clay, . 66.7 



Garden earth, . . 64.8 



Fine carb. lime, . 61.3 



Humus, . . 49.0 



Magnesia, . . 38.0 



It is seen that the sandy wsoils cool most 

 slowly, then follow clays and heavy soils, 

 and lastly comes humus. It must be re- 

 membered that the experiments were in- 

 stituted on dry soils, i. e., artificially de- 

 prived of water, and hence do not apply 

 to the soil in its natural state, in which 

 water is rarely absent. 



As to the rapidity with which various 

 soils become warmed by the heat of the 

 sun or of the day, no observations of any 

 agricultural value have been instituted to 

 m}^ knowledge. It is easy to speculate 

 upon this topic. The rapidity of cooling 

 appears to stand in direct connection with 

 the lightness and porosity of the soil ; 

 such qualities favor radiation, and the loss 

 of heat by the circulation of the inclosed 

 air. Such soils also, in nature, enclose a 

 considerable amount of water, and in them 

 capillary action is strongest in laising sup- 

 plies from the sub-soil. On account of 

 their porosity, this water is constantly 

 evaporating, and therefore by extracting 

 from them the heat necessary to vaporiza- 

 tion, their temperature is speedily reduced. 

 For the same reason moist soils rich in 

 humus, can warm but slowly in the sun's 

 rays. Sandy soils retaining little water, 

 evaporation is less active in reducing their 

 temperature. The surfaces of the grains 

 of sand are glassy and smooth, they there- 

 fore radiate poorly, though this depends 

 of course on the degree of fineness and 

 smoothness. Clays stand in the middle of 

 the scale. 



3. The degree of moisture present is of 

 great influence on the temperature of the 

 soil. All soils when thoroughly wet seem 

 to be nearly alike in their power of absorb- 



