674 GEOLOGY OF OHIO. 
Stone-ware should exhibit, on fracture, a blue uniform tint, and a 
semivitrified appearance. Different clays act very differently in this 
respect. 
Ware which does not vitrify can be picked out at a elanee in most 
places. The Roseville clay, asa rule, vitrifies well. Its composition 
may be illustrated by the following examples : 
1 2. 3 
Silica (Si O,) eo thal dele teteeeatesereuerncemcmenees 25.60 . 28.61 29.35 
Alumina CAleiOe Peon kctncsreceucteer ncumaceaecsssemnenes 19.08 23.01 23.05 
Water, combined (HE 1O) hi Seset cs nctileste neces Pghececest 5.57 8.03 7.89 
Sand (quartz) (SI, Os \ceosthectues tess cccoeceee teint ence 43.75 34.79 35.85 
Titanic acid (Ti O,) DAL EL Ee sdeu cotesnusaawattednenadcracasite te .29 35 5D 
Sesquioxide of iron (Fe, Og) ..............0s000 decimeccs 1.26 1.50 .99 
Dime! (Can @) Keeani cain cre scteccesessrsowanenstoudeescce ss .60 Al 58 
Wie vean eer), (Qui CO). c600500000600 0500606008 vadouoDad 066dH0 bac00C .63 .62 58 
Potash: (Rig) O)iia.cgetecweue ss weclosentmussmnoccciuestere ceeee anocen 2.14 1.26 1.45 
Stovoley enavel Iihdarkss (Onley, (©) eravol IVil, O)) <5/45006009 009 600000000 02 trace trace 
IMOIStUTE 2552522 eos cosceccomecteet uocoes gen Gostowcbeseunneaccees 94 Sel 1.11 
99.86 100.57 100.90 
1. Brummage’s Pottery clay (Lower Kittanning), Roseville. 
2. Allen’s Pottery clay (Lower Kittanning), Roseville. 
3. Uniontown Pottery clay, Uniontown. 
The potash is well up in each, and the iron moderate; and in all, 
the per cent. of fine quartz sand is very large. This is imperative in a 
stone-ware clay. The clays of this district make a very good ware and 
differ from those of the Akron district, in that their final appearance is 
due to the proper chemical changes having occurred in the burning, 
while the other clay seems to burn naturally to a close uniform body 
without undergoing much real fretting or vitrification. Plenty of 
Akron-ware showing a good color and to all appearance vitrified, is of 
a yellow tint in the fracture. This ware is glazed of necessity, for it 
will not hold water when unglazed. Nevertheless the quality of these 
wares is excellent, and it is not at all certain that a superior degree of 
vitrification would improve it. Its composition is partially shown by 
these examples from Myers, Atchinson & Co.’s clay bank, at North 
Springfield : 
