Page 3 Advertisements Column 1

Dominion, Volume 13, Issue 275, 14 August 1920, Page 3

THEGEINDING ■ I ar—w,ear-- • - Wasses ': ;' ■' '•■;.;..;'.,;.-.:";.';.'. ....' ,'.■ ■. ■:. 'Many people who wore.our old "Far-near" glasses—or tried to wear theni—were very conscious' o£' trouble. The marvel to lis is that so many people did wear them with comfort, and do still, because, optically, they are not at all; .right,. and yet they were the best that could ; be made, with the knowledge and facilities for'grinding lenses, avail- '• able some years -ago. ' '■■' ■'''■ ' ■■'.'■ '. •• : Of course; the obvious, defect'to. all, irearers and observers alike, is ' the line across the centre-where it-would be in the old Franklin bifocal, the "Perfection" or.in the'"Far-near"; but there is also a very ■ serious optical defect, and we want now- to show it to you. . IMPERFECTLY. CENTRED. To make a "Faivnear'' glass, we first of all/ground the distance. 5 lens. Then,,to get the reading, we ground 8 very thin lens, the focus : ' of. which represented the difference between distant sight and the reading. ..Then, we cemented-that Very thin lens on to the lower edge of the distant lens.-•■ ~- •- >■. . , , . Now,. notice the cross on .each kns, i indicating the optical centre of each. » f7 ..-..■■•■'. The distance remains correct. The op- '. *' \ • . tical ; centre of tlio reading lens, how- • 5 - ever, we cut away, necessitating sight < .for. reading through.'■ the ■ edge and not s '- through-the centre as it should be.' | '. ■';. The ■effect. of. this may be 6cen by S -.-■ looking at a straight line through the J -'• lower A-A!,..as seen through the reading { •. portion would be broken and lifted up \ ,',-: above the line, as seen through the dis- \ ,' *' ~ .. tance portion.. \ : CAUSED, IMPERFECT -SIGHT i ■■■'... Now, ,can see.. where the trouble came. People saw , j things out of their right positions. Steps seemed higher than they ' j . Teally were, causing many people to stumble. s ' ACCURATELY CENTRED j We have often illustrated the making of a "Kryptok" lens. 'We , 1 import the -two glasses fused 'together—a large slab of crown glass to - ' | which is fused to a small button of flint glass. That small.button is J .previously prepared,-and lias its own perfect centre, as has the distant | part, and when we grind them the line of vision disappears entirely. i I': "' '"■•'" .'-.-'»■•'■ ':..■'' . '' ' . | ' The glass looks like one, but has imbedded in it a small reading 3 ■ portion, possessing'a perfect optical centre, and the line A-A through H a-"Kryptok" lens appears, as .'hown in the. illustration above. | ! I .''.'■'• .'...'' ■'...'. i This'will suffice to show the great advantage,of "Kryptoks*' over I .... "Far-nears." : It does . away with the line, and.it gives a perfect op- if , tical condition. -.''.v... .'.". fi ■ The cost of,"Kryptokß" .should be-five or-ten times as much for I . the, old style, for they,are worth that much more. -As a matter of fact, i however, they cost very little more. We have mado. many hundreds 0 f "Kryptok" glasses, and we have ( . had., the utmost.,'6atiefaotionah-f l tting..them— that is to sav, our clients I . > have been satisfied,. and that, of course, is the only thing that consti-", \ '. tutes', bur .satisfaction'.,. . \..'.. . l 118 ;; r WELLINGTON - j , (Old Marble Bar Premises) , ' : \.".', \

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