234 
COMPOSITION 
ripening of fruits and fall crops. There is sufficient caloric retained to preserve the tempe¬ 
rature of the surface when the air is near the freezing point, provided the surface is covered 
and its radiation checked. On one occasion, the temperature of the air was reduced to 26°, 
while the soil beneath remained at 51° ; and although a severe frost followed this reduc¬ 
tion, yet many vegetables were preserved from destruction by the caloric which the earth 
had accumulated the preceding week, and which was then given off. This instance of the 
accumulation of heat in the soil occurred upon one of the high peaks at the head of the 
Delaware river, when the vegetation was just putting forth. On this mountain, the shrubs 
which had already leaved, or had partially leaved out, and some which had blossomed, 
were not in the least affected by the frost. 
The accumulation of heat often preserves the roots of corn, and other crops, when the 
herbage is destroyed. When the temperature of the surface is 60°, we have found that 
maize, planted however early, comes up ; while if planted when the temperature is several 
degrees lower, although later in the season, it will certainly rot. The temperature must 
reach the point of 60° in order to excite germination, which, if once secured, the grain 
seems to be safe, though it may not appear above ground for some time. 
From a few observations which we have made, it appears that mountain soils absorb 
more heat than the slopes at their base. 
The surface heat is often preserved in autumn by rain. In the spring, too, rains aid in 
warming the earth. A rain whose temperature was 54° fell when the earth was 49°, and 
the surface was raised soon after to 51°. 
The highest temperature of the ground, which has been observed, was 72°. This tem¬ 
perature has been maintained with little variation for several successive days, in August, 
the present year, 1846. The earth acquired nearly the same temperature about the same 
period last year. The water of a large cistern, whose surface is four feet beneath the sur¬ 
face of the ground, acquired the temperature of the earth, which it has maintained during 
the whole period of excessive heat. 
VII. COMPOSITION OF THE SOILS OF NEW-YORE. 
Several methods have been proposed for the analysis of soils, each of which has its par¬ 
ticular advantages. The method which has been followed in the New-York Survey has 
not differed materially from that usually followed in the analysis of a mineral. One hun¬ 
dred grains of the sifted soil is taken after it is dried in its envelope, and exposed to a 
temperature of about 300°, on a piece of glazed paper, or until the paper is slightly browned, 
upon a clean metal plate. The loss is set down as water. It is then exposed to a red heat, 
and stirred in a platina capsule, until its blackness has disappeared : thus its organic 
