Scientific amusements . roducing ?gaseous currents, and which will assist us in Our ScientificAmusements—viz., our ittouths ! Place a halfcrown flaton the table, then,seize it between two pins held at theextremities of the same diameter. You may raise it thuswith,out any trouble. Blow against the upper surface,and you will see the- coin revolving with considerablespeeid between the pins. The illustration (Fig. 3 5) shows the 46 DENSITY, HYDROSTATICS, ETC. manner in which this feat can be accomplished. The coincan be made to revolve (by blowing on its upper surface)with such rapidity as to make
Scientific amusements . roducing ?gaseous currents, and which will assist us in Our ScientificAmusements—viz., our ittouths ! Place a halfcrown flaton the table, then,seize it between two pins held at theextremities of the same diameter. You may raise it thuswith,out any trouble. Blow against the upper surface,and you will see the- coin revolving with considerablespeeid between the pins. The illustration (Fig. 3 5) shows the 46 DENSITY, HYDROSTATICS, ETC. manner in which this feat can be accomplished. The coincan be made to revolve (by blowing on its upper surface)with such rapidity as to make it appear a metallic this we have an illustration of the persistence of impres-sions on the retina, of which we shall speak hereafter. ; TO KEEP A PEA IN EQUILIBRIUM BY MEANS OF ACURRENT OF AIR. Choose as rounded a pea as you can find,. and softenit, if dry, in water. Then skilfully impale it on a pin,so as not to damage its exterior surface and get a pipe, of very small bore, and place the pea. Fig. 36.—Pea sustained in the Air by blowing through a Tube. on one of its extremities, where it is maintained by thepin which has been inserted in the tube. Throw yourhead back until the pipe is in a vertical position, andthen blow gradually and slowly through it. The peawill rise up; then blow more forcibly, and it will be,sustained by the current of air turning on itself when thebreath strikes the pin (Fig. 36). THE MOVEMENTS OF GASES. 47 Here is another experiment of the same kind :—Take a metallic penholder which is closed at one ofits ends. At a little distance from the closed extremitydrill a tiny hole. Then blow up through the aperture,thus formed, regularly and steadily. A small bread pellet,perfectly round, can then be kept up, as shown in theillustration (Fig. 37). The pellet should be as spherical as possible, its sizevarying with the density of the material of which it is
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Keywords: ., bookcentury1800, bookdecade189, booksubjectscientificrecreations
