. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. Fig. 220.—Lantern Galvanometer. Fig. 221.—Lecture Galvanometer is very little below the pivot e. Long or short coils may beused, and this pattern has the great advantage that it may beused as an ordinary lantern slide. In using any kind of face galvanometer, should the face D D 402 OPTICAL PROJECTION happen to lie in or near the plane of the magnetic meridian,it will he necessary to counteract the dipping-needle effectby adjusting a bar-magnet somewhere near, preferably under-neath the table
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. Fig. 220.—Lantern Galvanometer. Fig. 221.—Lecture Galvanometer is very little below the pivot e. Long or short coils may beused, and this pattern has the great advantage that it may beused as an ordinary lantern slide. In using any kind of face galvanometer, should the face D D 402 OPTICAL PROJECTION happen to lie in or near the plane of the magnetic meridian,it will he necessary to counteract the dipping-needle effectby adjusting a bar-magnet somewhere near, preferably under-neath the table. The most sensitive and precisely calibrated astatic galvano-meters are chiefly needed for very feeble thermo-pile currents,as in investigating the heat of the spectrum in its colderregions, or calorific interference bands (see Chapter XXIII.).Such a galvanometer is easily projected in the vertical manner,provided the base and dial-plate are of glass. The lecture galvanometers most generally used, however,where comparatively but not excessively small currents areto be demonstrated, are of the reflecting mirror class. Forordina
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
