. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. Fig. 2.—Hydrogen lens, (a.) this case, the outer annulus of the wave on entering the projecting sur- face of the lens g^ as at 4 and 5, would be hurried forward into a con- cave form, as shown at 5 and 6, having a general center of convergence at about e. On emerging from the second surface, /t, (supposed here to. Fig. 3.—Hydrogen lens, (&.) be a plane,) the wave, by oblique retardation, as shown at 7, would be somewhat flattened, as at
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. Fig. 2.—Hydrogen lens, (a.) this case, the outer annulus of the wave on entering the projecting sur- face of the lens g^ as at 4 and 5, would be hurried forward into a con- cave form, as shown at 5 and 6, having a general center of convergence at about e. On emerging from the second surface, /t, (supposed here to. Fig. 3.—Hydrogen lens, (&.) be a plane,) the wave, by oblique retardation, as shown at 7, would be somewhat flattened, as at S, 0,10, &c., extending the focal point of con- vergence to/. The eflect of a double concave surface to the lens would be to shorten the focal distance according to the degree of concavity. 2.—REFRACTION FROM INEQUALITY OF WIND, In 1857, Prof. G. G. Stokes showed that differences of motion iu the air must exert a bending influence on the beams of sound, and that this S. Mis. 115 14. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Board of Regents; United States National Museum. Report of the U. S. National Museum; Smithsonian Institution. Report of the Secretary. Washington : Smithsonian Institution
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