Show rUNS ROUND PEBBlES IN A YER YEAR Before 1911 1 practically a all the lie flint nt pebbles used in grinding processes b by metallurgic and amid cement mills in this countr country were Imported This was one of or the tho supplies for which the United States was dependent on Europe Now othe o the time United States geological survey sune department of or the Interior announces with wih satisfaction that approximately 1000 tons of grinding pebbles for tube mills mis L and OO tons of silica tube mill L were ana soia ola in Jim niS iii I country In Ul 1917 7 Besides these quantities quantities quant- quant ties of ot grinding pebbles an and Iner liners report reported re- re port ported d to lo the geological survey considerable con con- considerable unreported quantities of oC pebbles pebbles pebbles peb peb- bles and blocks of or rock and ore were collected used b by by- metallurgic and cement coment mills mils Tho The bureau of ot foreign anti and domestic commerce department of or commerce reports re report reports re- re ports port that tho the flint flints and amid flint flint- stones Imported for tOI consumption con con- In 1917 were valued at 9 This value represents about 15 tons part of which possibly 10 per percent percent cent was boulder flints ground for tor use In ceramic wares it J It thus appears that about tons of ot tube mill tube tube-mi lin lining ln- ln un- un ing Ine and grinding pebbles were used In Inthis Inthis inthis this countr country hi iii 1917 and that more than thanO 50 O per cent of the demand iemand was supplied I by bv materIals Artificially rounded blocks s o of rock made at Manhattan Nov e have been supplied to metallurgic mills mis near that town at prices cr very vary much lower than those of Imported flints and amid have nave proved satisfactory for grinding ln time the I ores of that region These pebbles are made from froni a rhyolite I which Is Js quarried and broken Into pol polygonal onal blocks that are arc rounded b by tumbling In a a. barrel like mill mi The Time tumbling also eliminates the cracked or weak calc blocks Grinding pebbles were gathered from tho the beaches benches between OceansIde and San Diego count county Cal Cat b by various individuals individual and firms Smooth round or nearly nearh roun round pebbles ran ranging inc I I In diameter r from two to seven se en inches aro picked out b by hand on tho the beaches and assorted according to size size I I |