X-rays and localisation / by James Mackenzie Davidson.

  • Davidson, James MacKenzie.
Date:
[1902]
Catalogue details

Licence: In copyright

Credit: X-rays and localisation / by James Mackenzie Davidson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    11/12 (page 11)
    state that there is also exhibited there an instrument for obtaining the stereoscopic image directly on the fluorescent screen. ^ On two occasions at the Soiree of the Koyal Society I have exhibited apparatus for giving the stereoscopic picture on the fluo- rescent screen, but, while interesting, they were too cumbersome for practical use. The problem to be solved mechanically was quite definite. Two tubes had to be placed opposite the observer's two eyes, the distance between the anodes preferably should be the same distance apart, namely about 6 centimetres, as the distance between the observer's two eyes. A fluorescent screen interposed midway had to be illuminated by one tube, and the shadow of whatever object was cast upon the screen had only to be observed by one eye, the other being eclipsed, then the next tube had to be illuminated and then the other eye only had to see the shadow produced by it. If this alter- nating arrangement could be repeated quicker than ten times a second the impression of the two shadows becomes continuous in each eye, the consequence being that the combined mental image stands out in striking stereoscopic relief. This diagram shows the principal fea- tures of the instrument which I am exhibiting in the Library. I have to thank my friend Dr. Muirhead for the help he has given me in the construction and designing of this instrument. A previous one was made for me by Mr. Crawley, representing Messrs. Muirhead, but which depended for its action upon two synchronous motors, but the latter instrument with the oscillating eye-piece is likely to super- sede the former. The practical value of getting a clear and brilliant stereoscopic image upon the screen is immense, for not only are the parts seen in their correct position, but when the apparatus is properly arranged, it is possible for the observer, with a metal probe, needle or forceps, to touch any object he desires which he sees in the stereoscopic image. [J. M. D.] I/lWnOM: pntNTRt) BI WILUAM OLOWM AND 80SU, LIMITED 0«1AT WINUMUJ, ajJJBKT, W.. AMD DOKB 8TBMT, BTAJU-OKU ilBEKT, B.B.