An Improvement in Magio Lanterns.
Year: 1891

page_text: Date of Application, 29th Oct., 1891
Complete Specification Left, 5th July, 1892-Accepted, 6th Aug., 1892
PROVISIONAL SPECIFICATION.
An Improvement in Magio Lanterns.
I, HERBERT CHARLES NEWTON Scientific Instrument Maker 3 Fleet Street
London E.C. do hereby declare the nature of this invention to be as follows:-
A method for the more ready & accurate adjustment of condensing lenses in
optical lanterns with relation to the object to be illuminated.
The adjustment being obtained by rack or screw motions carrying the condenser
& radiant.
COMPLETE SPECIFICATION.
An Improvement in Magic Lanterns,
I, HERBERT CHARLES NEWTON, Scientific Instrument Maker, 3 Fleet Street,
London, E.C., do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
In optical or magic lanterns, where large condensers are used to cone the light
down through the picture, of smaller diameter than the condenser, onto the
focussing lens, it is obvious that it is advisable to place the picture at such a
distance from the condenser, that the whole of the cone of light passes through it,
so that the utmost illumination may be obtained on the screen.
This object is sometimes attained by moving the slide forward till it reaches the
required position, and sometimes by moving both picture and front lens forward
together.
These methods, however, while providing adjustment for properly coneing down
the light through the slide, introduce disadvantages, inasmuch as there is a
disturbance of the picture on the screen, owing to the positions of the slide and
front lens in relation to the screen, being changed, during their adjustment, with
respect to the condenser.
This makes it very difficult to ascertain whether the alteration in position has
really increased the illumination, and hence these methods are not generally
used.
According to my invention, there is no disturbance of the slide and front lens
with regard to the screen, but I fix my condenser to a movable base on which the
jet also adjusts, so that leaving the picture and front lens in position, I can rack
the condenser and jet (without disturbing their relative adjustment) away from the
picture, thus obtaining the same advantage as by the other methods, without their
disadvantages, as I can rack the condenser and jet backwards and forwards to find
the best position, without affecting the picture on the screen in any way, except by
increasing its brilliancy.
In the accompanying drawing, I have illustrated a lantern embodying my
improvement,―
Fig. 1 being a sectional side view, and
Fig. 2 a plan, also in section.
The main features of the lantern are the same as those to be found in lanterns
already in the market, but the condensing lens A, instead of being mounted as
heretofore, is carried in a pair of brackets b b supported in the movable base B.

page_text: This base also carries the luminant C, and is capable of adjustment longitudinally
by means of a pair of racks d'd, engaging with rack wheels upon the transversely
mounted spindle D.
Thus, the condenser and the luminant, without disturbing their relative positions,
can be readily retired from the slide, in order to bring down the cone of light to
the diameter best suited for the picture to be shewn, while the slide and the front
lens remain undisturbed with regard to the screen.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
Mounting the condenser and illuminating jet of magic lanterns on a movable
base capable of adjustment to and from the slide, substantially as explained, for
the purpose set forth.
Dated the 1
TT 1000
NEWTON & SON,
Agents for the Applicant.