152 • CONDITION OF THE BONES. 



into and constitutes a part of many vegetables. It must, of course, enter 

 them in a liquid form, i.e. the form of a solution. If, then, we suppose the 

 bone of an animal to be situated in the vicinity of siliceous rock, near 

 others containing alkalies, — the latter, being dissolved, might unite with 

 the silex to form silicates, which, as fast as the decomposable animal matter 

 should be evolved, would readily penetrate the pores or cells left vacant 

 by the decomposed substance ; and the silicate, permeating the calcareous 

 matter of the bone, would gradually take the place of the animal texture. 

 Various experiments made by chemists and geologists demonstrate the 

 possibility of such an interchange. [Vide Professor Silliman's letter in 

 Appendix F.) 



The mineralization of organic substances contained in very ancient 

 deposits may, no doubt, be accounted for in a more satisfactory manner ; 

 since, in many of these, the agency of heat may be supposed to have been 

 introduced, and to have operated in the same way as in the great petrifying 

 hot springs in various parts of the earth. This process is perhaps one of 

 the causes which .have preserved to. us some of the bones of the Mastodon 

 Angustidens of the Old Continent ; but, as to the petrified bones of the 

 Mastodon Giganteus of the New, a different and more limited action seems 

 to have been exerted. 

 impregna- A part of the latter, however, appear to have undergone a degree of 



mineralization without petrifaction. I refer to those we frequently meet 

 with of a dark color, dense texture, and comparatively high specific gravity, 

 as is noticed in a number of the bones of the Baltimore skeleton, in those 

 contained in the collection of the University at Cambridge, and in others. 

 These are impregnated with a ferrugmeous solution, derived from the bog- 

 iron ore so abundant in various parts of the country. 



tion. 



