ONONDAGA SALT GROUP. 
131 
No. 53. 
stone, in being more smooth, and I have never seen the insterstices filled with calcareous 
matter. They are usually invested with a carbonaceous film, and present a black shining 
surface. 
The mode of formation in these bodies is supposed first to have been the crystallization of 
sulphate of magnesia in the fibrous form, shooting up in the same manner as water sud¬ 
denly congealed in a porous or spongy soil.* Common salt will also produce the same ap¬ 
pearance where the ground is saturated with it; and it would appear also that gypsum will 
take the same forms, and present many of the same phenomena of these lignilites.f 
The suture-like seams before spoken of usually occur as 
horizontal lines of division, the striated surfaces vertical. In 
the quarries at Mendon I observed some of these sutures in 
a vertical position, and the striated surfaces parallel to the 
place of stratification. The illustration represents the usual 
appearance of these seams when on a small scale. These su¬ 
tures sometimes separate, presenting a surface covered with 
toothlike projections. 
They will be readily recognized by any one after seeing 
these illustrations, and since they are known to be widely dif¬ 
fused and occurring in greater or less perfection in nearly all 
the calcareous strata of the system, and even in the higher 
rocks, they have become subjects of interest. The great 
limestone formation of the west, holding the place of the car¬ 
boniferous of Europe, and apparently identical with that rock, 
is marked by similar sutured divisions, and small columns like 
wooden pins driven into the rock. 
After leaving Mendon, this rock is not seen on the east side 
of the Genesee river ; the first point west of the river where it 
appears is on the “Street farm,” belonging to Mr. Wadsworth 
of Geneseo. The lower part is composed of thinly laminated strata ; the laminae often lighter 
and darker in color, giving to the mass a striped appearance, which is very common at many 
other places, and is one of those characters which serve to distinguish the rock at distant points. 
The upper part is thick bedded, of an ashen color, and contains irregular cavities sometimes 
filled with greenish clay; at others containing celestine, calcareous spar, and zinc blende. 
The more compact portions of the rock have been quarried and used for structures on the 
Genesee Valley canal. The following is the character of the strata as they appear at this 
place; there is no connexion with any other rock visible either above or below. 
Vertical suture in argillaceous lime¬ 
stone, Mendon, N, Y, 
* See Report Of Third District, page 107. 
f See an article in the American Journal of Science and Arts for Jan. 1842, by Dr. Locke, on some beautiful forms of 
gypsum discovered in the mammoth cave in Kentucky. 
17* 
