. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. re placed in the spring holder, and pro-jected as usual. This arrangement has been a great deal popularised inEngland by Mr. W. Lant Carpenter in connection with theGilchrist Lecturing Trust; and where actual physical apparatus,and diagrams, are the principal subjects of projection, it canhardly be improved upon for handiness, cheapness, and sim-plicity ; but it is not so well adapted for optical and acousticalexperiments, on account of the stray light. Fig. 82 is anAmerican modification of
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. re placed in the spring holder, and pro-jected as usual. This arrangement has been a great deal popularised inEngland by Mr. W. Lant Carpenter in connection with theGilchrist Lecturing Trust; and where actual physical apparatus,and diagrams, are the principal subjects of projection, it canhardly be improved upon for handiness, cheapness, and sim-plicity ; but it is not so well adapted for optical and acousticalexperiments, on account of the stray light. Fig. 82 is anAmerican modification of it, arranged with a special view to APPARA TUS FOR SCIENTIFIC DEMONSTRA TION 155 portability. The rails and legs are here dispensed with ; thelantern body is a mere frame hinged together, with a metaltop, and covered round when in use with thick black cloth; andthe whole is placed on a table. The jet is also modified forcompactness, the usual long metal tubes being dispensed the lantern is essentially the same as the Germanmodel. Lanterns of this type, either mounted on rails, or for. Pig. 82.—American Lantern simply placing on a table, with little unimportant variationsin detail, are now supplied by all the leading opticians. For optical experiments chiefly, and incidentally for otherphysical demonstrations, the most popular pattern in publicinstitutions till lately has been the well-known Duboscq lantern(fig. 83), fitted usually with the electric light. The squarebody is of sheet brass, and is mounted upon four brass is a flange-nozzle fixed to the body ; and the specialfeature of the arrangements is, that the condensers are fittedin the back end of a large tube which slides freely backwardsand forwards in this nozzle, the character of the beam being 156 OPTICAL PROJECTION modified by sliding the condensers to and from the light, insteadof moving the light to and from the condensers. An adjustableslit, and a circular revolving diaphragm of apert
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
