390 COMETS. 



of their grosser particles. From the essential 

 property of expanding which these parts pos- 

 sess, and from being situated in a medium 

 which affords to their expansible power little 

 or no resistance; it is a matter of necessity as 

 an effect immediately flowing from cause, that 

 the air, in its upper regions, should, in that 

 case, dilate to its utmost possible extent, and 

 diffuse itself to the uttermost regions of 

 space; so that all the materials on this earth, 

 which subserve to the . process of vaporisation, 

 would long before this period, have been dissi- 

 pated and elevated to distant worlds ; if there 

 did not exist means, by which those conse- 

 quences are prevented. We are, therefore, 

 driven to the necessity of searching for those 

 instruments, which a vigilant and protecting 

 Providence employs, and by which these de- 

 leterious effects are effectually averted. 



Without the existence of such instruments, 

 the whole economy of nature, would be sub- 

 verted and destroyed ; the planetary spheres 

 would be polluted, and penetrated by a con- 

 stant interchange of materials; they would 

 be rendered more dense, and more rare, at 

 different times. The planets, whose motions 

 are so regular and precise, would be either 

 accelerated, or retarded, in their course; 

 and neither their times, nor their revolutions, 

 could be anticipated, or ascertained. 



