. Annual report of the Board of Regents of the Smithsonian Institution . llows all the reliefs of the latter. These displace-ments of the style are magnified eight times by a lever near its lowerextremity; the end of this lever forms a minute contact which movesover the bars of a rheostat, R. The circuit incloses a battery, therheostat, R, the line and the receiving apparatus. According to thevalue of the relief at the point touched by the style, the resistancetaken from the rheostat is more or less great, and so the intensity ofthe current in the line varies. At the receiving station the appa
. Annual report of the Board of Regents of the Smithsonian Institution . llows all the reliefs of the latter. These displace-ments of the style are magnified eight times by a lever near its lowerextremity; the end of this lever forms a minute contact which movesover the bars of a rheostat, R. The circuit incloses a battery, therheostat, R, the line and the receiving apparatus. According to thevalue of the relief at the point touched by the style, the resistancetaken from the rheostat is more or less great, and so the intensity ofthe current in the line varies. At the receiving station the apparatusconsists of a galvanometer, O, whose mirror receives light from alamp. The pencil of rays reflected from the galvanometer falls upona lens so placed that the light which traverses it is always broughtto a focus at the point, F, upon the photographic film, A. Beforethe lens there is placed a screen, T, composed of twenty strips ofincreasing capacity, called by Belin a gamut of tints. Accordingto the deflection of the galvanometers, that is to say, according to the. Fig. 6.—Bellas apparatus. 204 ANNUAL EEPOKT_SMITHSONIAN INSTITUTION, 1908. n E I P n D u. -E intensity of the current coming over the line, the luminous penciltraverses a part more or less opaque of this gamut of tints andthe intensity of the light at F consequently varies. According as thereflected ray passes through a dark or clear part of the gamutwhen the style of the transmitter is upon a thin or white portion ofthe film will the result be a positive or a negative. The cylinder, C, of the receiver is inclosed in a dai^v chamber andcovered with a sensitive film. A metallic screen, pierced with a holeone-sixth of a millimeter in diameter, is situated at F and limits theextent of the film acted upon by this light. And finally, in order to avoid the phenomena of diffraction,a b this pierced, metallic screen touches closely the sensitive surface of thefilm. The reproduced image is formedby the juxtaposition of
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