ot 
What I am inclined to consider a case of this kind has lately 
been brought to my attention and I am persuaded to make a 
note of it the more for the purpose of correcting a grave error 
in investigation and one which is, strange to say, readily 
demonstrated to be an error. 
In 1867 (Amer. Jour. Science, Vol. XLIV.) Dr. G. 
Wetherill published a well-written and seemingly-exhaus- 
tive paper setting forth some “Experiments on Itacolumnite 
with the explanation of its flexibility and its relation to the 
formation of the diamond.” In attempting to elucidate the 
flexibility of this rock he has made use of the microscope 
and, in fact, mainly draws his conclusions from the revela- 
tions which he supposes that instrument makes. Some 
specimens of Italeolumnite, varying in tint from almost pure 
white to a rusty red tint and in texture from finely granular 
to coarse and distinctly laminated, having come into my 
hands, I have been enabled to examine into this point of 
structure and attendant flexibility, which I have done with 
some care. 
It is well known that Itacolumnite is the accompanient 
and often the matrix of the diamond, hence the interest which 
attaches to its peculiarities, as it would seem in some way to 
be connected with the occurrence or formation of that gem. 
Detecting dark colored grains in it Dr. Wetherill considers 
them to be black diamonds and doubtless he is correct in his 
supposition, but with this portion of his paper I do not desire 
to deal at the present time. It is with regard to the structure 
of the sandstone whereby it becomes flexible to the remarka- 
ble degree so evident when thin slabs are examined. The 
stone is plainly laminated and has clearly been thrown down 
beneath water, it being readily cleavable into more or less 
distinctly marked lamine. 
Almost universally the flexibility is attributed to the pres- 
ence of Mica but the brighter-colored specimens which I have 
examined contain no Mica and yet possess the property of 
being readily bent to a very marked degree. Even in the 
red-tinted specimens there are large portions in which no Mica 
is found. Dr. Wetherill says that by examining the Ita- 
