The Art of projection and complete magic lantern ... - Yesterday Image

—167planation we have indicated its principal applications to chemistry andphysics. We mention a few more experiments, as follows :A. Magnetic Spectrum. If we put glycerine in the trough, and if westrew iron filings on the surface of the liquid, the particles or scales ofthe metal will slowly descend into the centre.Let us introduce into thetrough the ends of an electro magnet, and send the current through itimmediately the descent of the filings ceases, and by degreesthey placethemselves so as to assume that special appearance to which the name ofspectrum inagneticum has been given. The successive interruptions andassumptions of the current cause the dissolution and the re-constitutionof the spectrum.B. Formation of cells. It is known that the cells of vegetable tissuehave a hexagonal form, and their process of formation which dependson the contact of the cells with each other (their first shape beingspherical), is thus demonstrated.Make a solution of some common soap in very pure water (i part ofsoap to 40 of water), filter it and double its volume with glycerine. Puta thin layer of that liquid in the trough, and produce soap bubbles byblowing through a glass tube with a taper end. The external cells willhave a rounded form, the interior cells a hexagonal shape. As the lightbecomes decomposed whilst travelling these minute liquid layers, thecells become coloured with all the hues and shades of the prism.c. Carbonic acid in the breath. The vessel being full of a well filteredsolution of lime water, on introducing a glass tube and breathing throughit, we shall notice that the water gradually gets turbid, and by this formationof carbonate of lime, the presence of carbonic acid in the breath isproved.D. Formation offrost. Dissolve sulphate of soda in warm beer in aslarge quantities as possible, pour the warm liquid on to one of the glassesof the trough with the pipette, spreading it out as much as possible \ ina few moments a series of foliage-like figures will have formed, whichmay well be compared with those which the frost produces on windowpanes.In this short notice we simply wish to point out the resources of thelaboratory trough. It may be seen how well it is adapted for a varietyof experiments. A few grains of salt, a few drops of a re agent, suffice