. Physical researches on sensation [by] Frank Allen [and others]. Fig. 2. round a long brass rod turning in a friction socket, also screwed tothe table. By turning this rod the string could be wound or un-wound, and the friction of the leather on the axle of the motor in-creased or decreased. With this simple friction brake, the motorcould be maintained constant at any speed from zero up to 1800revolutions per minute for a period of several hundred record automatically the speed of the disc a small handspeed-counter was clamped in a position so that its rubber tip. Fig. 3. press
. Physical researches on sensation [by] Frank Allen [and others]. Fig. 2. round a long brass rod turning in a friction socket, also screwed tothe table. By turning this rod the string could be wound or un-wound, and the friction of the leather on the axle of the motor in-creased or decreased. With this simple friction brake, the motorcould be maintained constant at any speed from zero up to 1800revolutions per minute for a period of several hundred record automatically the speed of the disc a small handspeed-counter was clamped in a position so that its rubber tip. Fig. 3. pressed firmly against the rear end of the axle of the motor (). The rubber tip served to prevent the relative slipping of motorand speed-counter, and to insulate the latter, which was necessaryas it carried a current. The small index on the counter was re- No. 5] PERSISTENCE OF VISION. 261 placed by a loiifj diametral arm, the ends of which in turn closedthe primary circuit of an induction coil at every fiftieth revolutionof the motor. The secondary circuit of tiiis coil passed throughmetal parts of a chronograph, with a narrow spark gap at the sur-face of the cylinder. At everj fiftieth revolution of the disc, there-fore, a spark perforated a piece of paper carried on the pendulum of a clock, by a mercury contact, closed the primarycircuit of another coil every second, and similar perforations weremade at these intervals on the same piece of paper. The time offifty or one hundred revolutions of the disc could then be easilymeasured, and the duration of thephysicalresearch00alleuoft
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectphysiol, bookyear1902
