Walls of JVorth-CaroUna, 5 



to Dr. Hall, would seem to me much the more rational and 

 philosophical, viz. that they are basaltic. Although the 

 position of these walls is in some degree an anomaly in the 

 history of basaltes, yet I think there is sufficient anaiogy 

 for the support of the opinion. The comparative analysis 

 by Dr. Woodhouse of these stones, rust and cement, (see 

 Med. Repos. Vol. 11. p. 259,) with those made by Bergman, 

 Monges and others, of the basaltes of other countries ; the 

 perfect unity in kind, of all the stones in the same wall, and 

 the near resemblance they bear to the specimens of basalt 

 in my possession, together with the following description 

 given by Cleaveland, render the thing conclusive in my mind. 



The most common colour of Basalt, says Professor 

 Cleaveland, " is greyish black, sometimes inclining to 

 brownish grey, and sometimes to brownish or bluish black ' 

 Some varieties have a tinge of green. The exterior is of- 

 ten brown, or reddish brown, in consequence of decomposi- 

 tion. The colour of its streak is a light grey. It is 

 opaque, or sometimes feebly translucent at the edges. Its 

 fracture is usually uneven or fine splintery, sometimes a lit- 

 tle conchoidal, earthy, or nearly even. It has no lustre, 

 unless from the presence of foreign substances. It is diffi- 

 cult to break, and frequently sonorous when struck. It is 

 more or less subject to decomposition, partly, at least, in 

 consequence of the action of the atmosphere upon its Iron, 

 which exists in a low state of oxidation, as is evident by its 

 action upon the needle. Hence the brownish, friable, or 

 even earthy crust, which often invests its exteriour. Those 

 Basalts, which seem to approach very near to green-stone, 

 decompose most rapidly. Indeed the whole mass is some- 

 times converted into an earthy, argillaceous substance." 

 Mr. C. however, thinks it extremely doubtful whether any 

 basalt, strictly speaking, has yet been discovered in the 

 United States, but that the columnar and prismatic masses 

 which exist in various parts of the United States, are un- 

 doubtedly a secondary basaltiform greenstone, which, in 

 some cases, may perhaps be passing into basalt. 



If then the fact be established, that these stones are ba- 

 saltic, I presume it will hardly be contended that they were 

 collected from, nobody knows where, to form a number of 

 parallel walls, of a length and depth which no man can cal- 

 culate. 



