Note on the stereophotochromoscope : a new optical instrument / by David Fraser Harris.

  • David Fraser Fraser-Harris
Date:
[1895]
Catalogue details

Licence: Public Domain Mark

Credit: Note on the stereophotochromoscope : a new optical instrument / by David Fraser Harris. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    A NOTE UPON THE VIBEATIONAL EATE OF THE MEMBEANES OF EECOEDING TAMBOUES. By David Fraser Harris, B.Sc. (Lond.), M.B., CM., F.E.S.E. (From the Physiological Laboratory, University of Glasgow.) Seeing that certain observers believe that the inertia of the lever and india-rubber covering of recording tambours {e.g., Marey's) is a source of error in tracings with these instruments, and seeing that these tambours have been widely used for graphic representations of movements of very different vibrational rates, I thought it well to attempt to estimate the period of oscillation of lever and membrane after mechanical agitation. I took an ordinary Marey's circular recording tambour (4-5 cm. diam.) covered with thin sheet india-rubber, stretched to medium extent, and carrying a light straw lever, 12 cm. in length, fur- nished with the usual short quill writing-style. The tambour was mounted on a heavy brass stand, and its quill touched the smoked paper of a drum rotating at the rate of 14 cm. per 5. The drum having attained full speed, I struck the table (a large, heavy one, screwed to the floor) with a violent blow of the clenched fist, in order to set up free oscillations of lever and india-rubber, according to their own proper period dependent on their inertia. Only the amplitude of the oscillations, not their rate, was altered with varying degrees of energy of blow. The blows were given at intervals, on an average, of -5, the amplitude of the initial excursion of the lever varying from 4 mm. to 1*5 mm. according to the violence of the blow. The period or vibrational-rate appeared by this method to be, on an average, 56 per 1; the tracings showing 10 vibrations per 5 mm. of paper with striking uniformity in a large number of trials. [Speed was 14 cm. per 5 .-.per r^cm.; 5 now in 5 mm. there were 10 oscillations .-. in 1 cm. . . 20 „