PLEASING DISCOVERY. 193 



in curing bewitched cattle." The reader will at once 

 perceive that the various objects referred to on this 

 and the occasions just cited were of precisely the same 

 character — they were, in fact, fossils. 



It is natural to inquire in what way such substances 

 are formed ; and in answering this question it will be 

 desirable to state some interesting facts in reference 

 to what is called petrifaction. Most fresh water, it may 

 be remarked, holds in solution a greater or smaller 

 quantity of lime, and various causes occasion the cal- 

 careous earth to be partially or wholly precipitated. An 

 instance of this kind occurs when a kettle or boiler 

 long in use becomes furred, the fur being the calcareous 

 matter which the water had contained. At the tempe- 

 rature of 60°, lime is fusible in 700 times its weight of 

 water ; and, if there be added to this solution a little 

 carbonic acid, a carbonate of lime is formed, and preci- 

 pitated in an insoluble state. When there is an excess 

 of carbonic acid, the lime again becomes soluble in 

 water, and thus carbonate of lime is commonly found 

 in all waters. When, therefore, the portion which 

 exists in excess is lost, the calcareous earth is set free, 

 and precipitated on any substance in the water. 



Some springs contain so large a portion of this earth 

 when they first issue from the rocks, that incrustations 







