For themselves, however, Joe and Blake got some fine views of a storm at sea, the waves being exceptionally high. The vessel rolled and rocked so that it was hard for the lads to keep their footing, but they were not seasick, which was more than could be said of most of the passengers. “In fact, there’s one gentleman who hasn’t been out of his stateroom since we started,” said the commander. “He wanted me to stop the ship, or else turn back, when we struck the first bit of open water. But you boys are real sailors.” Mr. Duncan, of course, was at home on the water, and he spent much of his time in company with the officers of the craft, swapping “yarns” of the deep. Joe and Blake spent some days looking over their moving picture cameras. They had purchased a new one in place of one of their old ones--a machine with several improvements. As I have designed this book to be instructive as well as entertaining, I will give a brief description of how the moving picture machine works. I presume you all know what a camera is. It consists of a light-tight box, with a lens for properly focusing whatever is to be taken. Back of the lens is a sensitized film of celluloid or a glass plate. When the image has been taken on this film, it is developed by chemicals, and when dry a print or “positive” can be made from it. And, for all this simplicity, it is a very wonderful process. A moving picture camera is merely another snapshot camera on a larger scale, except that instead of one plate back of the lens there is a continuous band, or celluloid roll. By turning a handle the reel of film passes behind the lens at the rate of sixteen small plates per second, taking this number of views of whatever moving or animated scene it is desired to show. A shutter, worked by the handle, alternately opens and closes just as you work the shutter of your small camera by pressing a button, and this shutter cuts off the view while a new section of film is pulled into place behind the lens. A moving picture camera can take pictures on a thousand feet of celluloid reel at one operation, and as each picture is only three-quarters of an inch wide, you can see that quite a number of separate views are possible. So much for taking the moving pictures. The operator points his camera at whatever he wants to show--a speeding train, a man diving, a scene in a theatre--anything he wants--turns the handle, and the rest is automatic. When the reel is filled with pictures it is developed just as you would develop a single plate, or film, except, of course, a larger tank is necessary. Many persons suppose that the film that is in the moving picture camera is the same one that is run through the projecting machine, and thrown on the screen. That is not so, otherwise it would be necessary to take many hundreds of reels of the same scene, to accommodate the many theatres.