HYDKOGEAPHIO KEPOKTS. 
91 
about four inches deep at the time of our survey ; and beneath 
that was almost everywhere a soft stone. Several loose speci- 
mens of pure limestone, and of limestone mixed with clay, were 
picked up on the beach, and accompany this report, as also a 
specimen of the sand taken from the bar. From the appearance 
of these stones they have evidently been long exposed to the 
action of the water ; and, from the feeling of the rock on the bar, 
I am of opinion that they are a portion of the same ledge — per- 
haps detached from it in the channel by some vessel's anchor, 
and afterwards washed up by the tides. If this be so, it will not 
only be practicable to deepen the channel over the bar, but the 
increased depth will remain permanent ; for this is the only bar 
(known to me) on this coast of rock formation, all the others 
being of shifting sand, sometimes covered with a deposit of 
mud, although their respective rivers have their origin and 
course in similar regions with the Coatzacoalcos. It would seem, 
therefore, that this ledge had been laid bare by the running 
waters, rather than that it should be the accumulation of ages of 
deposit. And this appears the more probable, inasmuch as all 
the local testimony coincides in representing the action of the 
freshets here to be one of removal, instead of, as at the mouth 
of the Tobasco River, one of deposit ; the layer of sand of which 
mention has been made, appearing only when the river is low 
and the current weak. 
In conclusion, I will take this occasion to say, that should the 
result of our labors be deemed satisfactory, it is because I have 
been seconded by such able and zealous assistants and men as 
those composing the Hydrographic Party. I am particularly 
indebted to Mr. Murphy for many valuable suggestions, and to 
all for their cordial co-operation. 
