BUILDING STONE. 115 
stone. This is the easternmost exposure of the last named stone. The 
Dayton limestone is a peculiar and exceptional member of the great 
Niagara series in southwestern Ohio. It lies in lenticular masses of 
comparatively small extent, perhaps not more than two or three square 
miles occurring in any one area. Throughout Montgomery and Greene 
counties the shale, which forms the next succeeding layer of the Niagara 
formation, has in almost all cases been removed by erosion, and thus it 
happens that the stone is immediately covered with the deposits of 
bowlders, clay, and dirt, as described. ‘he glaciers which have pro- 
duced this result have polished and striated the rocks in many cases. 
The composition of the Dayton limestone is shown from the follow- 
ing analysis, made by Dr. Locke in 1838: (a) 
Per cent. 
CAICIUMMCATWON ALO ctecree oe eccaes ee sca cece coe Lestion sesbiactostes sis divs deinstece recat 92.40 
IMIR OSSTUNTN | GAYE OXOTAENKE)46056509006 000000000 00000600000006000000000040500BD05000000 66 1.10 
Tron protoxide....... idroeececuise Sete cle las saodwacide se peaec cress tee sots edemeioee odode tn 0.53 
ImSoOlublepmaterialerecs mess cscc ccs cee crac was oonitewe eee eee. nore cece soc eweccctenes 1.70 
Soluublewsiltcaweretceeatensccccecocce hor teeta le stone dso ned au stone seanereeheveseate 0.90 
Witter nee eae ee Soe PE SNe at ee Sialic bts Be Se seeeeitahe 1.08 
PRO Gal Miawen eee cereus cs Seis cies nis Sohgcsdlosls seaeate solos e atieiueselis wean ecedeweeses 97.71 
The stone from the McDonald quarry, near Xenia, has been analyzed 
by Professor Wormley, (6) with the following result : 
Per cent 
SA CHUITMECAT WOM ALS Mma nectiens tee saneee ccc oe net ace aeee sae e ee eee cece oo roe nd duties 84.50 
IMAP ReSiIMACAT DONATE SMrn. tt sesradeaes cts conta ernest sohesieays tees: 11.16 
NUM AvaAM CEI OMNORUCE Le BE Eee deus caaktee cn wena neces eaeene 2.00 
SilRCCOUSMINNATLEIS secon c ete ihees acs eeeeaantsoe cae eer cab ee ae aie ed eeac deh dak es 2.20 
ARO LHDIL  caeicessu Barada Oooo I ACRE CE ICRC ET USE eta SZC ares in a a A 99.86 
When examined under the microscope these stones, as illustrated 
by the samples sent, are found to be composed largely of fossil fragments, 
which are so broken and destroyed as to be unrecognizable to the un- 
aided eye. ‘These fragments are united by an extremely fine-ground 
mass, in which here and there a sharply-definded rhombohedral form is 
porphyritically developed. These porphyritic crystals are quite promi- 
nent in the stone from the Huffman Stone Company’s quarry, near 
(a) Report of Progress upon the Geological Survey of Ohio, 1869, p. 152. 
(0) Geological Survey of Ohio, Vol. II. Part i, p. 669. 
