Footnotes

• 
  The only other example of this model known to exist is at the Science Museum, London. The following description is taken from the Science Museum catalogue where they state that "more than one may never have been made".
  
  Once an object had been lit, it could be rotated in any direction, vertical or horizontal, without losing its illumination - and that is no mean boast. To do this the object had to be exactly in the centre of all the circles in which the various parts were revolving; the result is this massive instrument, of which more than one might never have been made, for the theoretical shortcomings of oblique illumination were becoming apparent by the time it was produced. One cannot fail to be impressed by the virtuosity of the workmanship of this stand; the number of hours of handwork required to fit it must have been enormous, with cost correspondingly high. It works very well indeed, with the movements doing what was required in a precise, controllable and repeatable manner.
  
  
  The following description is taken from the Journal of the Royal Microscope Society 1887:
  
  Watson-Draper Microscope. - This Microscope made by Messrs. Watson & Sons, after the designs of Mr E.T.Draper is an elaboration of the instrument suggested by Mr E. Crossley. The following description is furnished by Messers. Watson:-
  The idea in arranging it is, that, when the object is on the stage, either it may be made to rotate in any direction, horizontal or vertical, round a fixed beam of light, without the light ever leaving the object, or the stage may be kept fixed while the light is revolving round it in any direction, horizontal or vertical; always, however, remaining on the object. Of course to do this exactly it is absolutely necessary that the object should be precisely in the centre of all the circles in which the various parts of the instrument are revolving, and to enable this to be done with the utmost precision, there is an adjustment to the stage by means of a micrometer-thread screw below, to raise or lower it according to the requirements of different thickness of objects.
  The body is mounted on an extremely solid pillar carrying a quadrant of a circle, and in this it may be placed in any position from the horizontal to the vertical, and as the stage is connected and moves with the body, and as this arc of a circle is struck from a radius, the center of which would be the object on the stage, it follows that when light is thrown from directly underneath the object, by inclining the Microscope through this arc and without touching the mirror, the light becomes more and more oblique, till it arrives at that point where it is impossible for it to enter the objective. Again, the stage being a concentric rotating one, allows the object to be moved horizontally round the same fixed light. The two motions therefore are used when it is desired to place the object in any position with regard to a ray of light.
  For those object, however, which could not be conveniently moved, there is another arrangement for keeping the object stationary, while the light is thrown upon it from any desired angle. This is done by using Mr Crossley's arrangement of a train of prisms transmitting light on to the mirror and rotating on an axis in the same plane with the object on the stage. The prisms have also the additional movement which Mr Crossley's arrangement has not, viz. the pillar supporting them is fixed upon a horizontal rotating base-plate so that by the movement of the base-plate, combined with the swinging motion of the prisms, the light may be thrown through them upon the object from any direction, horizontal or vertical. A lamp is fixed permanently to the pillar carrying the prisms, which moves with it in whatever direction it is placed. There is also a second lamp supplied for illuminating opaque objects from both sides of the instrument, so as to avoid the influence of shadows. The whole of the circles in which the various parts of the instrument revolve are graduated to degrees so that the observer may be able to tell the angle at which any effect has been produced in order that it may be at once obtained again.
  The substage and mirror are attached to the prism-box, and move with it. The mirror can also be detached and applied to the centre of the base.
  The stage can be raised and lowered to compensate for the different thicknesses of the slide.

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Category: Collectibles / Scientific Instruments

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