No. 200.j 
343 
From the circumstance that these rocks are an intermediate forma- 
tion, or produced at the change of a shale into a siliceous limestone, no 
two strata of it are alike. For example, an upper stratum may be 
nearly a pure limestone, while a lower one is almost wholly argillaceous; 
thus no reliance can be placed upon its quality. The same stratum at 
different places may also change the proportion of its component parts. 
The greatest objection in regard to the stone used for this cement is, 
that it contains too much argillaceous matter, and for this reason will 
never withstand the action of freezing water. Much of the cement 
now made is of very inferior quality, and losses are constantly sustain- 
ed from its use. This subject is one which requires strict and constant 
investigation, and the State of New- York would save large sums in the 
construction of her public works by procuring a cement of good quality. 
A cement required to withstand the action of freezing water, should 
contain little argillaceous matter. Clay, in any form, absorbs water 
abundantly, and if frozen while containing water, the cohesion of the 
particles is destroyed. By this process, every time it is frozen, a por- 
tion of the surface at least is removed, and finally the whole mass. 
The chemical composition of this rock is so variable in different locali- 
ties, and in different parts of the same locality, that this test cannot al- 
ways be satisfactory. The chemical composition of a rock, producing 
good cement, should be ascertained, and similar external characters may 
afterwards be relied on. 
A siliceous limestone, with a little iron or manganese in its composi- 
tion, appears best adapted for hydraulic cement. Limestone of this 
character can be found at intervals in either of the formations mention- 
ed ; but experience is necessary to choose the proper portions, and some 
localities afford an article far superior to others. 
The formations from which this limestone has been selected, extend 
across Monroe county from east to west: the one through the towns of 
Penfield, Brighton, Gates, Ogden and Sweden; the other through Men- 
don, Rush and Wheatland. At one locality in Ogden this limestone 
has been burned and used for cement in the locks on the Erie canal, and 
is said to have been of good quality. The same kind of stone may be 
found at the upper falls on the Genesee at Rochester. The best mate- 
rial of the kind which I have seen, is on the land of Mr. Miller in Pen- 
field. The strata are from tw^o to four inches thick, compact and sili- 
ceous. The location is near Rochester, and if it prove good and abund- 
ant, will be valuable. 
