218 ANNUAL' OF SCIENTIFIC DISCOVERY. 



The articulation is not that of basaltic columns. The component 

 grains are arranged so that most of the groups have cavities and 

 projections, and so that the projection of one group engages in 

 the cavity of its neighbor. Each group appears to be composed 

 of from 20 to 50 grains of sand not very strongly a'gglutinated : 

 the individual grains are very sharp fragments of silica, not flat 

 plates, and of great uniformity with respect to size. The scales 

 of mica are flat and nearly square fragments ; they average in 

 area (,08) 2 mm., and vary from (.26) 2 to (.065) 2 mm. 



"The most interesting relation of this rock is to the diamond 

 which it accompanies. This gem, found at first in the disinte- 

 grated rock, has at length been discovered in situ in the itacolumite 

 itself ; thus showing that this sandstone is at least one of the sources 

 of the diamond. 



"The physical conditions which have led to the peculiar jointed 

 character of the itacolumite may have had an important bearing 

 upon the crystallization of the diamond, and hence it is of interest, 

 to ascertain what those conditions were, with the hope of throw- 

 ing light upon the origin of the gem. 



" I confess to be at a loss to offer a very reasonable hypothesis 

 with respect to these conditions. It is difficult to see why the 

 siliceous fragments cohere to form definite groups or congeries. 

 It would appear that the sand which formed this rock contained 

 something diffused in a regular manner (and which was subse- 

 quently removed), which prevented the uniform contact of the 

 siliceous grains. It is possible to conceive that petroleum might 

 have that effect when added to sand of a certain degree of moist- 

 ness, forming a kind of emulsion, and that the petroleum was 

 afterward slowly removed by a process which permitted a crys- 

 tallization of a portion of its carbon. 



" I made this supposition before acquaintance with De Chan- 

 courtois's hypothesis that the diamond may have been formed 

 from hydrocarbons, and that its origin is thus connected with the 

 existence of petroleum-bearing schists. My hypothesis therefore 

 receives a certain support from the views of De Chancourtois. 



" I have heated several of my specimens of itacolumite to ascer- 

 tain whether any petroleum odor was evolved, but with negative 

 results. If the diamond proceeded from a slow and gradual oxida- 

 tion of the hydrocarbon, perhaps we should not expect to find any 

 petroleum left. 



" In this connection the small and rarely occurring black specks, 

 seen with the microscope, are to be noted. Are they minute 

 black diamonds, and have they any relation to the experiment 

 where the agate mortar Avas so deeply scratched ? " 



BAUXITE. 



At a recent meeting of the New York Lyceum of Natural His- 

 tory, Dr. Ferdinand Mayer made some remarks upon a new min- 

 eral which had recently been found in France, and was sold in 

 commerce under the name oT bauxite. It may be regarded as a 

 hydrated oxide of alumina, in which iron has been replaced by the 



