26 FIRST PRINCIPLES. 



fluid, is termed capillary attraction. Some fluids, mercury for 

 example, not only refuse to obey it, but even exhibit capillary 

 repulsion. The smaller and more numerous are the tubes or 

 interstices contained in a solid body, the more water will it be 

 capable of absorbing ; supposing that no chemical combination 

 (as occurs with quicklime and water, for instance) takes place 

 between the fluid and the solid. Hence, if we dip into water 

 two sponges of the same size, but of different degrees of close- 

 ness of texture, we shall find after we have withdrawn them 

 from the water and have allowed enough time to let all the 

 extra moisture drain away, that the sponge which has the 

 smaller interstices will have retained more water than the 

 other. 



As far as stable management is concerned, the subject of the 

 absorption of fluids by solids applies chiefly to questions of 

 bedding, stable construction, clothing and food. 



ABSORPTION OF GASES BY SOLIDS., 



" The surfaces of all solid bodies exert an attraction on the 

 molecules of gases with which they are in contact, of such a 

 nature that they become covered with a more or less thick 

 layer of condensed gas" (Ganot). As a great rule, the 

 absorbability of a solid for gases varies according to the 

 extent of its external and internal surface. Consequently the 

 more porous a body is, the greater power it usually has for 

 absorbing gases. In almost all cases, the easier a gas can be 

 liquefied by pressure, the greater capacity has it for being 

 absorbed by solids. For instance, one volume of boxwood 

 charcoal will absorb about 90 volumes of ammonia, 35 of 

 carbonic acid, and 8 of air. 



RADIATION OF HEAT. 



Radiation, in the sense used here, is the transmission of rays 

 of heat, or rays of heat and light, by a body without raising 



