With the way most trick-effects are produced in the studio the average writer need be little concerned except as a matter of interest.[19] The object of discussing them here is to show how certain plots, or parts of plots, are made possible as a result of knowing how these things may be accomplished, whereas without this knowledge the writer with a good idea might fear to include it in his story in the belief that it was impossible of production.  It may be remarked that what is said here has a bearing on Chapter XV, in which is discussed the matter of expense in picture production.  Some of the very companies who a few years ago were warning the beginning writer against introducing action that would necessitate too great an outlay of money are today producing features seemingly regardless of expense.  Yet most concerns are really exercising a wise economy and getting some wonderful results with cleverly planned trick-camera work.

[Footnote 19:  See Homer Croy’s How Motion Pictures Are Made.]

For example, in one episode of the Wharton serial, “The Eagle’s Eye,” the German conspirators in New York, seeking to injure the cause of the Allies and lay the blame on the American ’longshoremen at the same time, arrange to have a train of freight cars, crossing on barges from Manhattan to Jersey, dumped into the North River by removing the means by which they are held in place on the tracks of the barge and “letting ’em slide.”  The effect on the screen is wonderfully like what a long-range photograph of such an actual event would show.  All that was needed to produce the scene was a tank of water with a miniature barge pushed along by a tiny tug-boat, the latter steaming up very realistically.  When the toy barge and tug-boat were right in the middle of the “stage,” three or four toy freight cars were allowed to slide off into the water.  Above the tank, as a background, was hung some white or light colored cloth, making everything from the waterline up a white blank.  Against this blank was superimposed, by running the film through the camera twice, a picture of the New York sky-line as seen from the Jersey shore.  The unruffled surface of the water in the tank—­so unlike the wavy North River—­was almost the only thing to show certain of the spectators that the scene was not the real thing.  In another episode of the same serial, after the German spies have caused an Allied grain ship to be loaded on one side only, so that she will turn turtle as soon as released from her moorings, another very realistic scene shows the ship actually turning over, as much as the comparative narrowness of the slip will let her, after they have cut the ropes holding her to the dock.  Here, again, a model vessel in a built-up miniature slip supplied the means of obtaining a startlingly realistic effect.  The scene lasted only a few seconds, so that little opportunity was given the spectator to see how it was worked, but the effect of the brief scene was very convincing.