. Glasses for protecting eyes from injurious Fig. 12) transmits about 54 per cent of the infra-red radiation from a furnace heated to 10500 C. This is not a verymarked absorption when compared with the sage-green glass justdescribed. For the effectiveness in absorbing the ultra-violet, seeTable ^u. Fig, Crookess glasses: A, light (1= mm); B, dark (t= mm); C, ferrous , sage-green(t= mm).D, Schotts black glass (t= mm). E, white crown glass (t= mm). F, blue-green glass (A, O. No. 59; t= mm). (A and B are Crooksess neutral-tint glass.) Oth
. Glasses for protecting eyes from injurious Fig. 12) transmits about 54 per cent of the infra-red radiation from a furnace heated to 10500 C. This is not a verymarked absorption when compared with the sage-green glass justdescribed. For the effectiveness in absorbing the ultra-violet, seeTable ^u. Fig, Crookess glasses: A, light (1= mm); B, dark (t= mm); C, ferrous , sage-green(t= mm).D, Schotts black glass (t= mm). E, white crown glass (t= mm). F, blue-green glass (A, O. No. 59; t= mm). (A and B are Crooksess neutral-tint glass.) Other glasses were produced by Crookes which have a highabsorption in the infra-red. They are pale blue, bluish green, orsage green in color. In fact, as will be noticed presently, glasseswhich absorb highly in the infra-red have either a low transmissionthroughout the visible spectrum or have the transmission bandshifted into the green or blue. 8 Coblentz, Publication No. 97, Carnegie Institution of Washington, 1908. Glasses for Protecting the Eyes 9 IV. VARIOUS GLASSES FOR ABSORBING THE INFRA-REDGOLD-PLATED GLASSES Metals are the most opaque substances known for infra-redradiations, while in the visible spectrum (as is well known to allwho have handled gold leaf) gold has a region of low reflectivityand
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