178 COSMOS. 



its essential nature only acts dynamically, producing move- 

 ment and commotion ; but when it is favored at particular 

 points by the fulfillment of subsidiary conditions, it is capa- 

 ble of bringing to the surface material products, although not 

 of generating them like true volcanoes. Just as water, va- 

 pors, petroleum, mixtures of gases, or pasty masses (mud and 

 moya) are thrown out, through fissures suddenly opened in 

 earthquakes sometimes of short duration, so do liquid and 

 aerial fluids flow permanently from the bosom of the earth 

 through the universally diffused net-work of communicating 

 fissures. The brief and impetuous eruptive phenomena are 

 here placed beside the great peaceful spring-system of the 

 crust of the earth, which beneficently refreshes and supports 

 organic life. For thousands of years it returns to organized 

 nature the moisture which has been drawn from the atmos- 

 phere by falling rain. Analogous phenomena are mutually 

 illustrative in the eternal economy of nature ; and wherever 

 an attempt is made at the generalization of ideas, the inti- 

 mate concatenation of that which is recognized as allied 

 must not remain unnoticed. 



The widely-disseminated classification of springs into cold 

 and hot, which appears so natural in ordinaiy conversation, 

 has but a very indefinite foundation when reduced to nu- 

 merical data of temperature. If the temperature of springs 

 be compared with the internal heat of man (found, with ther- 

 mo-electrical apparatus, to be 98° — 98°'6 F., according to 

 Brechet and Becquerel), the degree of the thermometer at 

 which a fluid is called cold, warm, or hot, when in contact 

 with parts of the human body, is very different according to 

 individual sensations. No absolute degree of temperature 

 can be established above which a spring should be designated 

 warm. The proposition to call a spring cold in any climatic 

 zone, when its average annual temperature does not exceed 

 the average annual temperature of the air in the same zone, 

 at least presents a scientific exactitude, by affording a com- 

 parison of definite numbers. It has the advantage of lead- 

 ing to considerations upon the different origin of springs, as 

 the ascertained agreement of their temperature with the an- 

 nual temperature of the air is recognized directly in unchange- 

 able springs ; and in changeable ones, as iias been shown by 

 Wahlenberg and Erman the elder, in the averages of the sum- 

 mer and winter months. But in accordance with the crite- 

 rion here indicated, a spring in one zone must be denomin- 

 ated warm, which hardly attains the seventh or eighth part 



