CHAPTER III. 



GENERAL PROPERTIES OF GASES. 



GA& is an elastic fluid or air, formerly, but not now, supposed 

 to be produced by the union of some body with caloric: most 

 gases are inappreciable by the senses, except that of feeling, 

 having neither taste, color nor odor. Some have a specific 

 gravity greater, and others less than common or atmospheric 

 air. Several gases have been liquified by the conjoined action 

 of cold and pressure : several have also been solidified by the 

 conjoined action of intense cold and the pressure of from two 

 to fifty atmospheres. The product of this experiment is in 

 most cases an exceedingly transparent crystaline substance. 

 Gases, like, liquids, have but a slight power of conducting 

 caloric: their conducting power is so slight as to be imper- 

 ceptible, and they are therefore called non-conductors of 

 caloric. 



AH gases possess a certain amount of specific caloric, the 

 precise quantity which they respectively contain has not been 

 determined. Gases exist throughout nature, and may be 

 produced by artificial means. Some of them are capable of 

 being respired, without injury to health, while others cannot, 

 without producing deleterious or fatal effects. Some are, in 

 common language, supporters of combustion, while others are 

 not. Those gases only which are necessary to be known in 

 their relations to agriculture, will bo described in this work, 



