An Ancient Burg

[t'nmi the Scientiflo American.] In tho, current immbcr of tho Ovr.rland a California geologist reviews tlie geológica! eriaeBö of tho atitiqnity of a human settlemont ncar the present town of Chorokee, in that State, aml estimatcs the agc of that most aneicnt of diseovered towns to be not less tlian 180,000 years ! The data for all sucii calcnlations are necessarily uncortain, as tlicy are deriyed from the present motions of the continente and present raten of erosión ; still, from the changos that have taken place since the pioneers of prehistorie California loft thr ir traces on its ancient sea-shorc, thero can be no doubt that thousands of centurics must havo como and gone. Tho tracos in question are numerous Btotrce mor'jirfl, found in undisturbed whito and yellow gravel of a subaqueons formation, not iluviatilo, underlying the vast sheets of volcanic rock of whieh Table mouutain is a part. In one iustance a mortar was found standing upright, with the pestlo in it, npparontly just as it had been left by its owner. ■ In some cases tho mortftrp have been found at the depth of forty feet from tho surfaco of the gravel underlying tho Table mountain. Tho (Tiatritmttó oí (he mortars is suoh as to indicóte with groat positiveucss the former exÏBtenco of a human settlemont on that ancient beack ffren the water stood near the level at which tliey occur ; a timo anterior to tho volcanic Cmtpottring whic!i Table mountain records, and anterior to tho glacial epoeh. The recent geologioal history of that región may be briefiy summcd up as follows: l'revious to the plAoiaö oí the mortars in tho position iu which tliey have boon found, the early and middle tertiary eea levol had rceoded to the ])siti(ju oí tho coal beds underlying Tublo mountain, fully 1,000 iee brlow the level of Ohetokee. Subscquently, ia the plioceno pcriod, therc ivas a further aubsidence "f aliout 1,000 foei, Bomething liko 600 feeï occurring after I the mortars had been abandoned. All this, as has been noticod, took i)laco beforo the volcanio outilows which covorcd np all the ancient detritus of the región, including that of the ancient rivors (whose gravéis havo furnished so much of the gold of California). The geological age of tho river period was detorminod by Lesqueroaus from specimens of vegetatiou, nowextinct, collected in tho mivvoy of tho ancient rivers; specimens indicoting a llora of Ihe ]liooehé age, retáining some cliaracterisl'ic mioeene formn. After the volcanic period, tho land rose agnin, the time of emergenco embraeing the glacial period and the new eioding period iu the Sierra, during which the slatcs, and tho hard metamorphic greenstdnes, and the granitos were sjashed with canons 3,000 feet d!p by tlie ftoüon of ice Bnd running water. Taking the ratos of continental movemont determinad by Lyell, our geologi.?t calculates that the timo tequired for the changos thus outlined could not have boen loss tlin.ii eighteen hundred centuries. Por a period so long preoeding tho glacial epoch as tho timo when ancieut Cherokoe was buried by the waters of the advancin g sea, bis estímate is certainly not extravagant, though it does transcond so enormously the time men have been accustomed to allow for a man 's reeidenoB on earth.