| OCR Text |
Show VAnlATIONJ OFTMtOnCAT LA6S. The lllx ael I ell of the Wales I iluj b lllirereeeel l IUI..f,ll. Iboiiviatioiis in Hie lot els of the RrentUkes liato been the subject of study for ninny years put, nnd various tlu dries hat o been adv aneetl to aooouiit Inrtbeuu 'lhlrty years ago ull mail abla data rei.ardlii tbo lluotuatious were cotnplleil. sboaiu tho tnoro lm pirtant changes In the lower lakes bo Uvifiilttf-) anllSSr, wllh n few facts as to uiccptional pbnuuieim in earlier years. In IH, J tbo United States tit gluecrs begun systenmtlc gauge read lug" and the ork Is still cnuliiiuwl The lilf,beit known letel c-eourrod In 1688, when Michigan nnd Huron roo twenty six hirbvsabue ordinary lilgli stage and 1 rle an I Ontario eighteen Inches. Tho lowest 1st el tins In 1819, when l.rle Ml about three and a half fret below Its usual plane Tim Hue Illations, apart from the wlm.li arc minimi an I U10--0 caused by the winds arc of (lerludioal uocurreuc.-, anil are cliarncti rired by a remarkable approach to regularity Smro the highest waters f ISM there Imro ln alternate Iicriods of detotnlun and a-cvnslon n tit tiioletris, elllicrllvi', seltli or eight years In length, llio seven year pulud being tlio most frequent As wo ha.o sail, inrloin thenrlos liato been alranriHl to account for tbeso cliauges. Tbo winds, of course, cause teuiixiniryand local lliictiittions. I.rlc, tlie thallowcst of tho lakes, lias been known lo have lu lovil ral-ol eaten or eight feet at one end and equally depressed ut the other by n gnlo blowing cast or west for scleral dsys Irregularities and tarinllons of ntmixi Eberlo pressnro also cauochingos of irel, nnd tliero are tides on the likes us will as oil Ilia ooaan, the lilgliest ?;nown spring tl lo rising about three nclice, nun spot Influences, too, have been csslgneil as a causa of tho lluctu At Ions. Hatpins, liowover, to lu well esbib llslleil that tlie perlisllcal an I grnsnl lluctuatlons nro due to tlie variitlnns In rainfall. Ihe curves showing tlie secular arlatlons of lako lesel oppml linaloso clossly tothoMof raliifnll ns to show conclusli ely that tho rlw and fall of tbo lakes by rluds nf years am ilepende nt on tho cycles of rainy ami dry jcars, wblfli similarly coincide wilts the curves showing teiujiernturo cycle. A succession of viot cars produces exceptionally lilgti water, a ruccesilnn of ilry years extremely low wnter Them Is n limit, howover, to such uiimihtho oITocti, or nbon tho water Is high lis outflow Is liu.ro rapid than when it Is low, and an automatic t..cok Is thus prodded Toronto Mail |
