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A Trench Periscope sighting attachment for the SMLE rifle
Left: the front face of the prism
viewed over the rear-sight
from the muzzle of the rifle.
Below: the sight picture.
Looking up through
the base of the prism
over the sights
With the firer standing on the fire-step, the rifle would, most commonly, be rested on the trench parapet, ideally on a sandbag,
or similar, for stability and to protect the right forearm, then held with the right hand holding the wrist of the
butt-stock and with the fore-finger on the trigger in the usual way.
The left hand would be used to grip the butt-plate, with the left fore-arm above the head.
Sighting could then be accomplished by tilting the head back and looking through the underside of the prism.
In March 1915, Youlten was granted a further patent for a modified prism design,
now additionally in the name of the company Periscopes and Hyposcopes Ltd.
In January of that year he had already patented a design, no. 480,
for a hyposcope which could be "attached to the backsight of a machine gun".
Periscopes & Hyposcopes, Ltd.,
and Youlten, W. March 4. Sighting - accessories:-
Consists in forming a hyposcope of a single prism having (1) a front face normal to the line of sight, (2) a first reflecting-surface which is total-reflecting, and (3) a second reflecting surface which is silvered or otherwise converted into a mirror. In the prism shown in Fig. 2, the reflecting surfaces 19, 18 make angles of 60 degrees and 90 degrees respectively with the front face 17, and the ray is deflected through 60 degrees. In the prism shown in Fig. 6, the reflecting-surf aces 24, 23 make angles of 45 degrees and 112½ degrees with the front face 22, the ray being deflected through 45 degrees. A prism constructed according to this invention may be combined with other reflecting-surfaces which first deflect the sighting-line sideways and then backwards.
Youltens' inventive ideas for sighting aids were prolific, and he subsequently designed an elaborate rifle optical system along the lines of the Lattey, Neil and Gibbs Galilean products, but again also for possible utlisation on a machine gun.
This unit received its patent grant in August 1915.
11,227. Youlten, W. Aug. 3. [Cognate Application, 1163/16.]
Sights; sighting-accessories: -
Relates to optical sights of the kind in which a half object lens or com¬bination, and a half eye¬piece lens or combination are so mounted with re¬spect to the Ordinary sights that an open sight can be taken and, at the same time, a magnified image can be seen. Accord¬ing to the invention the object lens is mounted in a carrier adapted to be clipped or otherwise attached in close proximity to the foresight, and the eyepiece lens is mounted in a carrier adapted to be attached to the V or equiv¬alent part of the backsight so that it moves there¬with. Figs. 1, 3, 4, 5, and 6 show the invention applied to a service rifle. The eyepiece lens t, Figs. 3 and 4, is mounted in a carrier s provided with clips 2, 3 and a screw, 4 for securing it to the ordinary V sighting plate, in such a position that the bottom edge of the lens is level with the top edge of the sighting-plate. The object lens h, Figs. 5 and 6, is mounted in a carrier g fitting, by means of a dovetail joint, in a base-plate formed with a clip a, b for securing it to the gun. Figs. 8 and 9 show a method of securing the eye lens 13 to the backsight of a machine gun. The lens is mounted in a carrier 12 which is attached to a plate 8 adapted to be clipped to the sighting-plate. The lenses may be adjustable. A hyposcope may be combined with the eye lens.
Although the patent for this particular device was acquired early in the First World War, there then being a genuine need for such equipment, a similar unit had been offered to the military for assessment ten years earlier. This former device received a favourable report after trials, and the archives of the School of Infantry's Weapons Collection - to whose curator we are grateful for permission to replicate the material - contain the minutes of the relevant Proceedings of the Small Arms Committee. Item number 103 (SIGHTS), of minute reference number 712, replicated below, details the report and conclusions.
PROCEEDINGS OF THE SMALL ARMS COMMITTEE.
26th January 1903.
MINUTES 712 TO 714.
ROYAL SMALL ARMS FACTORY,
CHIEF INSPECTOR, WOOLWICH - ‑
CHIEF INSPECTOR OF SMALL ARMS ‑
NAVAL MEMBER - ‑
SUPERINTENDENT, ROYAL LABORATORY ‑
DISTRICT INSPECTOR OF MUSKETRY,
DEPUTY ASSISTANT DIRECTOR-GENERAL OF
ORDNANCE (0. 7)
* On leave.
Mr. Youlton's proposed Hypo-telescope.
Previous Minute 705 v.,
D.G.O., 23.1,1903, forwarded the following description by the inventor of his proposals — improvements on the hyposcopes previously submitted :—" The range-limit of the rifle hyposcope used at Bisley, and tried at Hythe, was 600 yards. The latest model has the following advantages :—
" 1. It can be used at any range shown on the backsight of any rifle.
" 2. Shooting may as accurately be continued without the ordinary rifle backsight
as with it ; equivalent to an additional backsight should that on the rifle
be rendered useless.
" 3. The elevation of the hyposcope equivalent for the rifle backsight can be accurately, and at once, effected by a screw. This is placed several inches below the rifle backsight, so that the needful elevation can be obtained without moving the rifle from any rest, or exposing any part of the marksman to the enemy.
" 4. A lateral wind-gauge is provided on the hyposcope. As this is quite independent of the V of the backsight, a man may, without lowering his or taking his finger from the trigger, instantly aim in a different direction to that for which he may have made wind allowance ; for in the eye-mirror-of the hyposcope, both the movable wind-gauge (vertical) line, which acts as a backsight, and the fixed V, are visible—thus either may be instantly utilised at will.
" 5. In full view of the marksman is a table of wind allowances.
" 6. The tube of the new instrument is square, instead of round, the field of view (6') being therefore much larger.
" 7. Any ' cant' of the rifle from its vertical axis is visible in the sighting focus.
" 8. A reliable telescopic sight is also added, for which the elevation scale of the Backsight
is mechanically (not visually) utilised.
" Up to 2,000 yards, a ' Hypo-marksman' can now take steady aim, with his head
as well as body in perfect safety below any available cover from 12 inches upwards, with the choice of using his natural vision, or (in one second) a reliable telescopic -sight. He also possess the advantage of a fired wind-gauge and ' cant ' indicator, as well as the additional backsight mentioned.";
Mr. Youlton attended the meeting to further explain details.
The committee are of the opinion that this is an instrument very well designed for its purpose and suggest that a small number be purchased and issued to commands for trials, and report as to whether such an instrument would be a useful addition to the soldier's equipment for service. It is for consideration if this instrument would not be a useful addition to the equipment of permanent fortifications either in its rifle or ordnance form.
E 2302. 50 & 4.--2/03, Pk. 399, E & S.
VIEW THE ABOVE ARCHIVE AS A PDF
See also the Chandler Periscopic Hyposcope Lee-Enfield rifle adaptation
For Enfield and Lee-Enfield training rifle accessories and adaptations, see also: Miniature calibre adapters and conversions
Should you have an unusual Lee-Enfield small-bore rifle conversion and be willing to provide photographs, then we would be grateful to receive details.
Full acknowledgement of any published images would be afforded.
email the editor: HARC-MRL@rifleman.org.uk
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