194 



WRITINGS OP JOSEPH HENRY. 



[1855- 



water, aud afterwards plunging them separately into equal 

 amounts of cold water of say 32° F. It will be found that 

 the heat which they severally impart to the water in the 

 two cases will be very different. 



The following table, also from Becquerel, gives the relative 

 retention of heat by different soils, (that of calcareous sand 

 being one hundred,) and also the time of cooling of cubes of 

 3'2256 inches (550 cubic centimeters) of the different earths. 



Table of retention of heat, by Becquerel. 



Effect of Cold. 



While the periodic temperature of a given place de- 

 pends upon the position of the sun in its course, the abnor- 

 mal hot and cold periods, or terms, as they have some- 

 times been called, are due principally to winds from certain 

 directions. The cold terms in this country generally begin 

 in the northwest and advance southerly and easterly, and 

 are accompanied with winds from the north and northwest. 

 We do not however intend in this place to discuss these 

 abnormal variations of temperature, but to consider the 

 effect of cold on different bodies, including plants and ani- 

 mals. We shall first consider its effects on a surface of water. 



Efed of cold on water. — When the surface of water is ex- 

 posed to a low temperature, the upper stratum is cooled, 

 becomes specifically heavier and sinks. A lower portion 

 then comes to the surface which in its turn is cooled, be- 



