BUILDING STONE. 641 
selves in a ground mass, giving to the stone a porphyritic aspect. There 
are the compact fossiliferous stones and the compact non-fossiliferous 
stones. As regards colors, they vary from very light to very dark, but 
all possess the drab, gray, or yellowish tints which are characteristic of 
what are called limestones. 
In microscopic structure the limestones of Ohio can all be classified 
according to certain types of structure which are found to be correlated 
with composition. It may be at first remarked that the microscope 
indicates that the stones are all highly crystalline. A crystal is a body 
which possesses a definite internal molecular structure, and if it is further 
assumed that the external crystalline form is a property of crystals, then 
many Ohio limestones are more crystalline in their structure than are 
the so-called highly-crystalline marbles; for in a great many cases the 
very well developed crystals with external planes are developed in the 
mass of the stone, and in other cases the stone is entirely composed of 
such crystals with the form characteristic of the species of the mineral 
which composes it. In no case has there been found in any Ohio lime- 
stone anything which could be called in any correct sense of the word 
uncrystalline; and indeed, in the light of microscopic study, any 
distinction which can uniformly distinguish a limestone from a dolomite 
is very difficult to find. The progressive increase in the amount of 
magnesia which is contained in stones is indicated in the microscopic 
structure by the development of little rhombohedral erystals the sections 
of which appear quite conspicuous with their sharply-defined edges. 
Nore. 
From the statistics gathered by the tenth census of the United States, it appears 
that Ohio ranks first in the value of building stones quarried in 1880. There are 250 
quarries in the state, the output of which exceeds $1,000 annually. The follow- 
ing interesting table was prepared by Mr. T. C. Keily of the Smithsonian Institution, 
for “ The Builder,” of May, 1883. 
The States producing building stone in 1880 rank in the following order as to 
total production of all classes of stone, the value given being that of the stone in the 
rough at the quarry: 
PROT OR cnet mee ca hate cenctisdsniwcenutertectet atiuusscusis'cosessustaeeees $2,541,647 
24, IPE KVERITIEY ooconon Ga RESO AOOARHONGHA bd00r atc DERN a Rete cece ee pene 1,944,208 
SMILE TIM OM Canwecainaiey soca nes don oes esiesisiieit seis ssistne odescabens dad seceicades 1,752,333 
Ae VIASSAC MUSE LES acancnatoesseecce caccinccioec an icicoc dessececesecessceseesss dee 1,711,104 
41 G. 
