209 



Dr. C. T. Jackson tliought tliat the smoothness and absence of 

 indentation showed that no change had taken place in the forms 

 since tlieir deposition ; they are perfectly polished, as in the stones 

 rolled upon our shingle beaches by the powerful action of the 

 surf; this constant grinding, and rolling up and down, by the 

 force of the waves, would produce various cylindrical forms, and 

 even the crooked and distorted ones exhibited on the diagrams of 

 Mr. Hitchcock ; and similar shapes can be seen any day upon the 

 present beaches. Beside, quartz pebbles could hardly have been 

 softened by heat, and, if they were, would have taken different 

 forms from these. The magnetic iron he considered the result of 

 a metalliferous emanation, rising in vapor, as in almost every vol- 

 canic eruption, and requiring less than a red heat. They were 

 parallel to each other and to the line of the strata, because they 

 were thus formed originally. In presence of sea-water, a moder- 

 ate heat would be sufficient to cause the pebbles to be united by 

 a cement of Wollastonite or silicate of lime. He was averse to 

 any theory of their explanation which requires softening after 

 their deposition. 



Dr. A. A. Hayes gave the following, as the result of 

 his examination of the mineral substance, found by Dr. 

 C. F. Winslow, occupying the medullary cavity of trees 

 growing in the Sandwich Islands. (See page 190 of the 

 present volume.) 



Plnjsical characters. This matter occurs in the form of hollow 

 and sometimes solid, cylinders, about one fourth of an inch in 

 diameter. Small lateral holes are found opening into and through 

 the cylinders ; and the color, externally brown, is yellowish gray 

 when freshly fractured. 



The hardness is greater than calc-spar or dolomite, and nearly 

 that of fluor-spar. Specific gravity 2.414, and general appear- 

 ance that of imitative forms of brown iron ore. 



Analysis. Boiling distilled water dissolves an organic salt of 

 lime, and the solution has a strong earthy odor. 



Carbonate of soda solution takes up crenic and humic acids. 

 There are no other acids or bases present. 100 parts consist of 



PIIOCEEDINGS B. S. N. H. VOL. VII. 14 MARCH, I860. 



