The Astrophysical journal . r, — a trifle larger than theplatinum foil, is dipped in a solution of shellac and applied tothe strip. The superfluous shellac solution is brushed off. andthe bubbles of air between the platinum strip and the papercarefully removed. After a completedrving, the glass plate is fastened tothe table of a dividing machine, andthe platinum strip is cut up into piecesof proper width, which afterward caneasily be separated from the glass plate. Two such strips lying next eachother are tested as regards their electricresistance, and if the difference be-tween them is not mo
The Astrophysical journal . r, — a trifle larger than theplatinum foil, is dipped in a solution of shellac and applied tothe strip. The superfluous shellac solution is brushed off. andthe bubbles of air between the platinum strip and the papercarefully removed. After a completedrving, the glass plate is fastened tothe table of a dividing machine, andthe platinum strip is cut up into piecesof proper width, which afterward caneasily be separated from the glass plate. Two such strips lying next eachother are tested as regards their electricresistance, and if the difference be-tween them is not more than a few percent., they are fastened to a smallebonite frame R (Fig. I, in natural size). On the paper sideof the strips the thermo-element is fastened by means of a littleshellac, and in such a manner that the junctions L lie about atthe middle points of the strips. The thermo-element consists of aU-shaped piece of a very thin sheet (about mm thick) of* constantan or nickel, to which is soldered a plate of cop-. ELECTRIC COMPENSATION PYRHELIOMETER 335 per of the same thickness and width. In order to comj^lete thesymmetry for power of radiation of the back sides of the strips,these sides were coated with black varnish. In order to blacken the strips on the front sides, they were first coated galvanically with a thin layerof zinc, and then treated with aI per cent, solution of platinumchloride until the resistance, whichhad been slightly lessened through^^ coating with zinc, reached its former(/Hj value. In order to raise the coefifi-cient of absorption, the strips werefinally given when cold a thin coat-ing of lamj)black. This coating wasobtained from a stearin candle, inthe flame of which was held a finenet of copper wire. The readinessof the strips for use is tested bvconnecting the thermo-element to asensitive gah^anometer. If the posi-tion of rest of the galvanometerdoes not chance for simultaneousradiation upon the two strips, the symmetry is complete. The juou
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectspectru, bookyear1895
