CHAPTER XIX. 



CIECLES. 



IT was before shown that the constant Expansive and 

 Contractive forces, particularly illustrated in the previous 

 chapter, call into requisition the law of Circulation, which 

 gives form to the motion of particles impelled by the 

 previous forces. By circulation is meant a proceeding from 

 a given point or condition, and finally returning to the same, 

 whether the line of progression described by the movement 

 is mathematically that of an exact circle or not ; as is illus- 

 trated by the flowing of blood from the heart, through various 

 channels back again to the heart. 



But it is here to be particularly observed that the blood, in 

 passing from the heart, through various parts of the system 

 back again to the heart, deposits certain portions of its ele- 

 ments in various fleshy and osseous tissues along its path. 

 This example, taken from the functional operations of the 

 Microcosm, or little universe, serves as a sure index of similar 

 operations which occur in the various departments of the 

 Macrocosm, or great universe, and leads to the remark, 

 that all regularly circulating materials, whether in the human, 

 the animal, the vegetable, the mineral, the geognostic, or the 

 astronomical department of creation, impart certain of their 

 elements to the ambient spaces through which they pass. It 

 is by the aggregation of such imparted elements that all 

 regularly developed forms in nature have their being ; and as 



