. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. ant ofchanging. By having one end of the panoramic carrier cutinto stops at different distances from the end, different sizescan be used after each other and still be centered. On rare SLIDES, CARRIERS, AND EFFECTS 139 occasions this is an advantage, but the panoramic carrier hasno other merit in my opinion. If different sizes have to be shown in the same lecture, thebest carrier is probably that known in the trade as Beardsself-centering carrier, shown in fig. 73. Whatever be thesize of the
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. ant ofchanging. By having one end of the panoramic carrier cutinto stops at different distances from the end, different sizescan be used after each other and still be centered. On rare SLIDES, CARRIERS, AND EFFECTS 139 occasions this is an advantage, but the panoramic carrier hasno other merit in my opinion. If different sizes have to be shown in the same lecture, thebest carrier is probably that known in the trade as Beardsself-centering carrier, shown in fig. 73. Whatever be thesize of the slide, it has only to be placed upon the brass runnerat the bottom and pushed up till it stops, and it will be in thecentre of the stage. The best and simplest carrier for any single lantern, orbi-unial, is, in my own opinion, the simple one shown in fig. 74,but it is only possible for slides of uniform size. There aretwo grooved frames with openings at the top, into which slidescan be dropped, the two combined sliding freely from side toside in an outer frame which remains immovable in the Fig. 74.—Double Carrier There is a stop at each end, so that when the inner framesare pushed up to either end, one frame is centered. The slidedone with is out on one side, and can be lifted out by thefingers and the next one dropped in, at any convenient dropped in it is ready, and a push in changes the slidein an instant. To prevent the dropping in of the slide makingany noise, it is well to jam in a narrow strip of india-rubber{flat) on the bottom of the bottom groove. This carrier is an especial comfort to the scientific lecturer,especially if he has himself to stand near his lantern, as oftenhappens. The assistant has only to concern himself to havethe next diagram ready in the frame not in use ; and can thenbring it on in place of the other in the twinkling of an eye, or MO OPTICAL PROJECTION the lecturer himself, if standing near, can do it with a touchof his ha
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
