. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. d up first, before thecurrent passes, with no result; afterwards the filings willadhere, and show an evident tendency to range themselves atright angles to thecurrent. To explain theconstruction of anelectro-magnet, twosmall solenoids ofinsulated wire arearranged across asmall frame as in fig. 226, being wound in contrary directions. They shouldbe wound so much apart that the turns can be clearly stout needle may be first introduced into each, and a mag-netised needle, sus-pended at o
. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. d up first, before thecurrent passes, with no result; afterwards the filings willadhere, and show an evident tendency to range themselves atright angles to thecurrent. To explain theconstruction of anelectro-magnet, twosmall solenoids ofinsulated wire arearranged across asmall frame as in fig. 226, being wound in contrary directions. They shouldbe wound so much apart that the turns can be clearly stout needle may be first introduced into each, and a mag-netised needle, sus-pended at one endby a thread, may beshown to be equallyattracted by either;then on passing thecurrent, it will beattracted by one andrepelled by the otheras shown in thefigure. Withdraw-ing the needles, andintroducing a smallhorse-shoe of an-nealed iron wire (fig. 227), we have an electro-magnet, whosewhole construction is clearly seen, and which will support anail or other piece of iron easily. Magnetic hysteresis can be shown by any electro-magnetsmall enough for the field of the lantern, or by a larger one. Fig. 226 4o6 OPTICAL PROJECTION
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Keywords: ., bookauthorwrightle, bookcentury1900, bookdecade1900, bookyear1906
