Having obtained the positive film, with its string of consecutive pictures, we now proceed to reproduce upon a large scale the animation which has been, so to speak, harnessed by the camera. For this purpose three essentials are necessary—a projecting apparatus, a powerful and brilliant illuminant, and a white surface or screen, upon which the pictures are thrown.

In its general appearance the projector resembles the magic lantern, which before the advent of the cinematograph held the field as a favourite source of amusement. It has the small box or cabinet in which the light is placed, and the condenser whereby the rays from the illuminant are converged into a powerful beam to be thrown through the picture and the lens upon the screen. This part of the apparatus is practically the same as that required for the purpose of showing still-life lantern slides. It is the mechanism required to bring the consecutive pictures singly before the lens in rapid succession that constitutes the real difference between the modern projector and the old stereopticon.

The projecting mechanism has the same task as the camera for securing the pictures. That is to say, a small section of film corresponding to the dimensions of a picture has to be brought into position before the lens in such a way as to permit the powerful concentrated beam of light from the lantern to pass through it and throw an enlarged, brilliant, and clearly defined picture upon the screen. The image rests on the screen for the fraction of a second, to be followed by the next picture. One does not observe the change from one picture to the other, as there is a revolving shutter, the opaque blade or blades of which cut across the screen at regular intervals. While the shutter is passing the lens, thereby interrupting the passage of light to the screen, the succeeding picture is brought into position; and when the opaque blade has passed, it is exposed in its turn and makes way for the next picture, this alternate action continuing until the end of the film is reached. It will be seen that an intermittent motion has to be given to the film in projection, in precisely the same manner as is required in the camera for exposure.

Although the evolution of a smooth-working and perfect camera taxed mechanical ingenuity to a high degree, the proportions of the task were not to be compared with those involved in the design of the projector. Many factors had to be taken into consideration. In the first place, it was imperative that each picture should be superimposed exactly upon its predecessor, that when the image reached the sheet it should stand as steadily and as still for the minute fraction of a second as if it were a lantern slide, and that the change from one picture to the other should be carried out in such a way as to render the change as imperceptible as possible to the spectator. In short, every effort had to be made to reproduce by intermittent motion the effect obtainable with the camera obscura.

The perfection of this illusion has demanded years of unremitting experiment and research. When animated pictures first came before the public they had a violent flickering, oscillating, and jumping motion, which proved exceedingly painful to the eyes. The effect was somewhat similar to that produced by gazing at a picture which is vibrating, and blinking rapidly meanwhile, or when a flicker-disc is rotated very rapidly before the limelight centred upon a stage scene and actors.

By dint of persistent effort and the perfection of mechanical details, this serious flickering and jumping effect has been eliminated; that is, so far as is possible with an apparatus designed to convey the impression of continuous motion by intermittent action. The projecting mechanism is of substantial design, while the moving parts subjected to wear and tear are made of the strongest metals. The wear and tear, however, is tremendous, and as all the moving parts are liable to displacement they must be fitted with adjusting devices whereby all slackness can be taken up and the apparatus be kept tuned to a high pitch of efficiency. Great ingenuity has been displayed in the conception and manufacture of these details, and the cinematograph projector of to-day is a wonderful piece of mechanism.

The optical principle of the cinematograph is exactly that of the magic lantern. Reference to Fig. 9 will explain it fully. The illuminant is represented by L and the centre of the light is opposite the centre of the condensers C C, which receive the rays and condense them, the point of convergence being in the lens or objective O, from which they pass out in the form of an expanding cone of light to fall upon the screen. The rays in passing from the condensers penetrate the picture F on the film in position before the lens. It will be seen that the lens has to be mounted so that its longitudinal axis is level with the light. The distance of the light L from the condensers, and similarly the distance of the lens or objective O from the picture F is governed by the focus of the objective.

It is obvious, therefore, that the picture to be projected must be brought to a stop in a position central to the lens, and for this purpose there is a film trap or gate, where it makes a momentary halt, in precisely the same way that the unexposed film is arrested in its progress through the camera.

The film to be projected is carried upon a spool mounted on an arm or bracket above the mechanism, with the pictures upside down as in the ordinary magic lantern. The spools used are of the open or the closed type. The former is permissible in countries where there is no rigid legislation governing cinematograph displays, or where non-inflammable films are used; but in Great Britain the film must be wound upon a spool enclosed in a metallic case, to provide protection against fire. The best spool boxes are lined with asbestos, which ensures a greater degree of safety.

From the spool the film is threaded over a toothed sprocket, which engages with the perforations, and also under a spring grip roller which keeps the film in contact with the sprocket. A loop is then formed, and from this the film passes into the gate behind the lens. This gate consists, as in the camera, of two pieces, one rigid, the other swinging and hinged to the first, so that it may be opened to enable the film to be introduced. When closed, the film is held flat and rigid. As the shutter passes across the field of the lens, cutting the picture off the sheet, the film is given a sharp jerk downwards to bring the next picture into exactly the same position in the gate before the lens as that occupied by the preceding image. The descending film passes round a second toothed sprocket, with its grip roller, and thence into the second spool box, where it is coiled upon the bobbin. The machine is operated either by hand or by power and belting passing over a pulley.

I have described the broad principle upon which the projector operates; the details of the mechanism vary according to the ideas of various makers. There are several excellent projecting mechanisms on the market, each possessing departures in detail, to some of which reference is made later.

The great difficulty was to impart intermittent motion to the mechanism which feeds the film to the lens at regular intervals from a continuous rotary drive, the handle being revolved at uniform speed. It occurred to Paul, who was the first man in England to attack the problem scientifically, that it might be feasible to employ the type of intermittent gear used in watches, known as the Geneva stop. He decided to adopt this mechanism.

The driving wheel when it completes a revolution falls into a notch of the driven wheel, and in continuing its rotary movement moves the latter forward the extent of one notch, but no more, owing to the convex space between each notch, or concave rim of each tooth, which coincides with the curve of the driving wheel and fits closely against its circumference. When the driving wheel makes its second revolution it engages with the second notch, and so on, with the result that in this case the driving wheel makes seven revolutions to one of the driven wheel. Each notch coincides with a picture; that is to say, each time the driving wheel forces the second wheel forward one notch, a picture on the film is brought before the lens for projection.

This novel gear gave the desired result, but it underwent considerable modification, the number of teeth in the driven wheel being ultimately reduced to four. The driving wheel was also altered. Instead of being notched as in the Geneva stop movement, it was fitted with a pin, which, when the wheel made a complete revolution, fell into one of the deep notches in the driven wheel, and so moved it forward. By this modification the gearing was reduced to 4 to 1; the driving wheel made four revolutions to one of the driven wheel, and each notch of the latter corresponded to a picture. Owing to the fact that the notches in this driven wheel resemble a Maltese cross in form, the device became known as the “Maltese Cross” movement. It is in use to-day. The notched Maltese cross wheel is attached to the spindle of the sprocket wheel below the lens, and the movement forward of one notch suffices to jerk the film down smartly three-quarters of an inch or the depth of one picture.

The advantage of this movement is that the film is pulled down very quickly, and as a result the flicker is reduced to a negligible quantity. The gear is noiseless and enables a very steady picture to be obtained upon the screen. On the other hand, not being a true mechanical movement, the forward motion of the film is accompanied by a certain degree of shock, which not only imposes a strain upon the fragile film, but at the same time sets up great wear and tear in the mechanism itself.

For these reasons another system of bringing the film into place was evolved. A wheel having an eccentric movement is introduced below the film gate. This wheel carries a projecting roller, and with each revolution the roller strikes the film which passes over the wheel, and pulls it down the depth of a picture. This type of action is known as the “dog” movement, and is incorporated in a variety of ways for the purpose of facilitating the smooth and regular movement of the film through the gate. Its disadvantages are that it is noisy; and secondly, that it is almost impossible to secure a steady picture upon the screen, as the dog strikes the film so smartly as to set up a vibration which is communicated to the picture in the gate. But it is simpler than the “Maltese cross” movement, while the wear and tear upon the mechanism itself is so slight as to be almost non-existent.

These two movements have divided the cinematograph world into two camps, one adhering to the “Maltese cross,” the other staunch in its support of the “dog” movement. But the former appears to be increasing in favour, despite its acknowledged defects. Some years ago Paul indicated an improvement on it which demands attention because it converts an indifferent mechanical movement into one scientifically correct. The principle is shown in Fig. 10. Instead of having four notches or slots in the driven wheel, as in the Maltese cross, he has only three slots. The driving member A has an arm C carrying a roller E at its outer edge. The driving member A when it completes a revolution, enters the slot c in the driven wheel B, and at the moment of entering the slot is at a tangent to the circular path a of E, with the result that the roller E enters the slot without setting up any shock whatever, carries the wheel B round, and leaves the slot at a similar tangent to its path, at the same time bringing the next slot tangent to the path of the roller E on arm A. Thus the film is given increasing speed without the slightest strain, and as the movement enables the images to be changed rapidly without jarring, it is possible to reduce the period of eclipse to almost nothing. For this reason, the opaque sector of the shutter can be cut down to one sixteenth of the area of the circle described by the shutter. With the other movements the sector of the shutter must cover at least one-quarter of the superficies. In other words, the three-slot wheel cuts down the period of eclipse to less than one-quarter of that possible by any other mechanism, and as the sector only covers one-sixteenth of the circle, the period of light thrown through the film on to the screen is increased, with an accompanying increase of brilliancy and a complete absence of flicker.

The shutter is one of the most important features of the projector. In the majority of cases it is placed before the lens, but in the Gaumont “chrono” machine it is placed between the condenser and the picture. In order to secure the best results, the area of the opaque surface covering the lens while the next picture is brought into position should be reduced to the minimum, and the eclipsing action should be so carried out as to reduce the flicker, which is directly due to the cutting off of one picture to enable the next to be brought into position. In the early days the shutter had one blade only; when a brilliant light was used, the alternate periods of light and darkness could be easily distinguished, and the eyes suffered accordingly. An effort to remedy this disastrous effect was made by the introduction of a violet-coloured sector of similar area to the opaque sector, and set opposite to the latter, which gave the shutter the appearance of a two-bladed propeller. This is effective to a certain degree; but it has been superseded by a shutter having three blades. The shutter is mounted upon a spindle in front of the lens, the distance therefrom being determined by the focus of the objective.

The heat concentrated upon the film by the converging rays of light from the condenser is tremendous. The effect is identical with that produced by focussing the sun’s rays with a lens upon a piece of paper. If the rays are permitted to play upon one part of the celluloid film for four or five seconds it will become ignited. So long as the film is moving little apprehension need be entertained; the danger arises when the film is stopped to attempt focussing with a stationary picture, or the film breaks during projection and stops in the gate. Several disastrous catastrophes have arisen from the firing of the film during projection. It is impossible to lay too great a stress upon the danger, for the average operator is little more than a cog in the machine, and fails to concentrate attention upon the work in hand so as to anticipate and meet emergencies.

Manufacturers have tried to remove the danger by the evolution of what is known as an automatic safety cut-off. This is a second shutter, which, when the projector is at rest, drops between the light and the lens. The shutter is connected to the balls of a governor. As the revolving speed of the governor is increased by the turning of the driving handle, the balls assume a horizontal circle of rotation, and in so doing, lift the shutter until it rises clear of the aperture in the gate, through which the light strikes the picture. In the same way, as the revolving speed of the governor is decreased, the balls fall and the shutter descends.

The introduction of this automatic cut-off is somewhat to be deplored. It makes the operator less careful; he trusts blindly to his automatic friend, which, though it functions admirably, is, like all such mechanisms, liable to fail at a critical moment. When such a breakdown does occur, the average operator is invariably caught napping, and the film is fired before he realises what has happened. The older system, whereby the cut-off, a shutter working upon a hinged flap principle, had to be operated manually, was far safer. Its opening or closing constituted a part of the cycle of operations in the preparations for projection, thus calling for a definite movement on the part of the operator.

The most efficient safety appliance yet associated with the projector itself is the Urban-Joy-Harris anti-firing device, Fig. 11, a very simple arrangement, whereby the rising and falling gate is converted, to all intents and purposes, into a fire-proof box. When the film is threaded through the gate, only that part before the lens, upon which the light rays are converged, is exposed to the air on the side nearest the light. On the opposite side the exposure hole is contained in a tube, holding the lens, which consequently forms an air-tight chamber upon that side. Should the film catch fire while stationary in the gate, the air contained in the lens chamber A becomes heated suddenly, and expands, so that the products of combustion are discharged through the exposure hole of H into the air. The fire cannot creep up and down the film, as small bars exactly above and below the exposure hole successfully prevent such action.

In addition there is the Harris safety shutter, which in the event of the film breaking below the gate, and thus preventing its own passage owing to the interruption in the driving effort, shuts off the light from the film, and also stops the electric motor, should the machine be driven by electricity. This safety-shutter B holds a semi-circular flap D, which is connected by a small lever to a rectangular flap C. The flap D is so adjusted as to hang over the loop in the film E between the sprocket and the entrance to the film gate. Under normal conditions the loop E does not come into contact with the shutter D, but when the film F becomes broken below at K, the loop E is enlarged suddenly owing to the film not being able to pass through the gate, with the result that it forces the flap D to a vertical position, and this in turn throws the flap C down over the exposure hole. There is a tube I which contains about half-an-ounce of mercury with an electrical contact at either end, the object of which is to change the centre of gravity of the flap D, and also to cut off the supply of electric energy to the motor. When the machine is running smoothly this tube I is in a horizontal position making the electrical connection at either end, but when the flap D rises, owing to the enlargement of the loop E in the film, the weight of mercury is thrown to one end of the tube, causing it to cant in such a way as to retain the flap D in a vertical position. If the film should take fire, only the picture before the lens is consumed. Even the perforated edges remain untouched, so that the film is not severed, and can continue its travel through the machine when the breakdown is repaired.

To supply the light necessary to projection, acetylene, the oxy-hydrogen limelight, and the electric arc have all been used; but the last is the illuminant most generally favoured. It enables the maximum amount of light to be collected by the condenser. When the projection of moving pictures was first attempted an arc light was unavailable, because that form of lighting had not been adapted to the magic lantern. The late T. C. Hepworth, the eminent authority on the lantern, was wrestling with the problem, but there was no commercial apparatus suited to the cinematograph. In using electric light a resistance is required to absorb or dissipate in the form of heat the current over and above that required for the light. Many types of resistances have been devised for this purpose, to suit varying requirements. This method of dealing with the surplus current is, however, distinctly wasteful, and accordingly, where picture projection is being carried out on a large scale, a motor generator is adopted. The current derived from the supply main is utilised to drive an electric motor, which in turn actuates a dynamo, whereby current is furnished for the light. This seems a roundabout process, but it effects a great economy in the consumption of electricity.

The mounting for the lantern is also important. As there is continual movement in the mechanism owing to the communication of driving effort, either by hand or by power, the mounting chosen must be of a sufficiently massive character to absorb all the vibration set up. Paul devised an iron pillar, to one side of the top of which the lantern was fixed, while the projector was attached to the other. The principle was similar to that used for the mounting of a machine gun, and although the idea met with considerable criticism, yet Paul succeeded in producing steadier pictures than were possible with other forms of mounting. That his idea was sound is witnessed to-day, for the principle he advocated has been resuscitated in the Brockliss Motiograph, which is mounted on a rigid pillar, and undoubtedly throws a steadier picture than is possible from any other system of supporting the projector.

In the majority of projecting mechanisms a second lens is mounted upon the frame, in line with and beside the cinematograph objective. This second lens is used for the projection of lantern slides for the illustration of a song, title announcement, or other purposes. In order to bring the light of the lamp into line with this second lens the lantern is moved bodily sideways the requisite distance; the projector itself is not touched—it remains a rigid fixture.

Paul also adopted a driving system which might be revived profitably to-day where manual operation is practised. Instead of the small handle placed somewhat high, calling for quick rotation and fatiguing wrist movement, he used a large wheel mounted at such a height that the operator, when standing beside, had the lowest travel of the handle almost at arm’s length. The wheel being of large diameter, a slow, steady revolution was sufficient, which caused no fatigue, the drive being transmitted through a pulley or chain to the projector. In many of the latest picture palaces, however, the apparatus is driven by an electric motor, which yields a more uniform speed and conduces to steadier projection.

I will now take up the distinctive features of some of the best known makes of projector. A comparison of the latest Edison model, the “B Underwriter,” with the first kinetoscope, affords a striking illustration of the advance of cinematography in twenty years. The new machine is constructed throughout of metal, is wonderfully compact, and the mechanism has been reduced to the acme of simplicity. All moving parts subject to heavy wear and tear are made of lignum vitæ. The shutter is of the three-bladed type, while the intermittent action is conveyed by the Maltese Cross movement. Being rigidly mounted upon a heavy stand, the picture projected is very steady and free from all disconcerting lateral and vertical movement.

In the “Gaumont Chrono” projector, the salient characteristic, as I have mentioned already, is the position of the shutter, which is placed between the film and the condenser. The film-trap is worthy of notice because it conduces very materially to the steadiness of the picture thrown with this machine. The edges of the film are gripped by means of burnished steel runners or vertical clamps, and they secure it in position during exposure with the exact degree of tension required to obtain steadiness, yet without hindering the travel of the film through the gate, or inflicting injury upon the celluloid. The trap is fitted with an asbestos shield, which serves to insulate the film while passing through the trap from the intense rays of the light, which is continually playing upon the metal around the exposure hole.

The dog movement has been adopted in this apparatus, but upon an improved principle. Instead of striking the film one smart blow to jerk it through the gate, it imparts a steady pushing action. The result is that the film does not suffer any injury. A massive dog striking the film heavily is apt to produce cracks across the perforations at the points of impact, which in time become weak spots in the film. This well-conceived machine has met with remarkable popularity among moving picture theatres in this country; it is an excellent example of French engineering skill, wherein lightness is combined with strength and simplicity.

The Ernemann “Imperator” projector commands deserved attention. It is built stoutly so as to last and withstand rough usage. Steel forms the constructional material throughout, and a noticeable feature is that motion is communicated to all driving parts through heavy gearing. In this machine the “Maltese Cross” movement has been brought to its highest pitch of perfection, being of large substantial construction, and so designed as to obviate the objections to its use. The driven part is made of hardened silver steel, and there are means of taking up all slack arising from wear directly it becomes manifest. Instead of the cross being struck by a pin on the driving wheel, the latter carries a roller which picks up the slotted wheel without jar or noise. The mechanism is kept cool by running in an enclosed oil bath, which tends to reduce the wear and tear to a minimum, while at the same time the machine is light and easy running, a feature which appeals to the operator.

Another machine which possesses many interesting points is the “Silent Knight,” its chief claim to attention being, as its name implies, quietness in running, combined with easy operation and steadiness of the pictures projected. It has the fire-proof gate already described, and also aluminium fire-proof spool boxes. The movement is the Maltese Cross. Simplicity has been studied to the last degree, and the necessity to withstand hard wear and tear, as well as rough handling in inexperienced hands, has not been overlooked. All the vital parts are made of chilled steel running in an oil bath, with the necessity for adjustments reduced to the minimum, though capable of being carried out easily when the necessity arrives.

The foregoing by no means exhausts the variety of machines on the market. There is the Pathé machine, a masterpiece of French manufacture; the Kamm projector, the “Empire,” remarkable for its many ingenious devices to secure protection against fire, the chief of which is a contrivance whereby the light is cut off automatically in the event of the film breaking, although the machine is still running, and so on. In every instance the direct aim is the evolution of a projector which will produce an absolutely steady picture, free from flickering and fluttering, and as noiseless in operation as human skill can contrive. In this particular field England and the Continent are ahead of the United States manufacturers. Except in one or two instances the American product is distinctly inferior. It looks attractive, but its results fail to stand comparison with the British and French machines. The projecting features of the moving picture industry in the United States have not advanced to the high state of excellency attained in Europe.

In projecting, the pictures have to be thrown upon the screen at the same speed as that at which they were taken by the camera, that is, if steady continuous motion is to be secured. The average speed is, as I have said, about sixteen pictures per second, and it is essential that the handle should be rotated at a regular uniform pace. Outside influences appear to exercise a distinct effect upon this manual action, just as we have seen them do in the process of taking the original picture. The musical accompaniment is likely to induce the inexperienced operator inadvertently to accelerate or retard the speed of projection. For this reason, power driving is coming more and more into use, the motion being communicated to the mechanism by means of a small electric motor. The results are far superior to those produced by the average operator, though not comparable to projection by a practised and intelligent hand. The latter can tell the approximate speed at which the pictures were taken, and can adjust his speed to a far greater nicety than is possible by a mechanical agency which maintains a constant speed.