| OCR Text |
Show the Wtrm UuciK a 't ' f4 ler rl'4havelong" a Ueli ar J invariable standir') M r 'li Th meniunvs in oomiiion uu bp m irl l trar length, and If tie rlglr il st u I anls should I dertrord ' l I not I accurately replieed. Tli Trench met-i U Mipl-ovd to bo a ten millionth rt of tlte quadrant of tlteenrlli, but the aontrauy of thoorlfltial ttieatunmient bare been seriously enlled In question Tlierefon. tlioeooatlod 'wave Inngth of light have been suggested as funii-1 Ingan Invarliblfltiuuierloal inngnllude but their eteeeflvit tnlnuteneM and t'i dlfdculty of aeourntely measuring tliem bare hitherto been on objection t their tiso. Hut ll la enld (hat a method 6t mea urlng these warolength, hlcli la at ei.rnto to tho one (en millionth part lias been illeeuvemd When It Is eon kldrrrd that n wave lontfli of sodi urn (yellow) light Is cmty About 0 forty tboiisan ltd of an Ineli, the rx tremo detlen y of this method becomes apparent 1iateicr theory may 1m licllas tol.ie natyro of light, tie mi tncrlcAl rnhieA oailrl wnv lengths for convenience are acttul and Inva r table representative nf fomething and If tho proiM! new method of meauunynenl proves reliable, lhre will 1 no KUlAully In obtaining a fit d standard n( length which can be rewv-ducod rewv-ducod at any time or lace. |
