��Popular Science Monthly
���At left: The Bettini camera with plate-holding magazines in position for taking motion- pictures. The amateur may make his own negatives and develop positives for pro- jection upon the screen. A special device can be fitted to this camera for taking photographs
��At right: The disk projec tor intended as a toy for children. Here the mo- tion-pictures are printed on a flexible non-inflam- mable disk instead of on glass. The disk may be held stationary for any length of time required for a detailed study or adjust- ment of any of the pictures
���and the lantern for projecting it on the screen) are moved across each succeeding row in the opposite direction. In other words, the lens or lantern is moved from right to left across the first row of images until it comes to the last square, when the glass plate is automatically fed downward to bring the second row into position, and so on until the plate has been used. The feed of the Bettini apparatus is so constant that the pictures are projected with very little flicker.
The synchronizing of the plate movement and the lens move- ment is so perfect that there is no "jumping" when the glass plate is shifted down from row to row. Further- more, one plate may quickly follow another, so that the longest picture may be pro- jected as easily as with the celluloid film.
The optical principle of the Bettini plate camera and pro- jector — the principle on which all the patents are based — may be understood from the accom- panying diagram. The objective with its prism is mounted on one side of the plate, while on the other side is a second prism on the longitudinal axis of the lantern con- denser. The light from the lantern passes through a condenser, strikes a prism iand is there bent at right angles toward the image on the plate. Passing through the image on the plate it enters the lens to
���which the prism is attached, and once more the ray is deflected at right angles so as to be thrown upon the screen.
Any image on a Bettini plate can be enlarged and printed in a few seconds. The plates may be run backwards, thus afford- ing no end of amusement. Circular sheets of non-inflam- mable material may be used instead of glass plates, and cir- cular and square plates may be made from standard films.
��The combined camera and projector. The plate movement and the lens movement are so perfect that there is no "jumping" when the plate is shifted down from row to row
��A Trip to the North Pole by Submarine
AS early as 1899, Mr. Simon Lake, the inventor of the "Lake" type of submarine, proposed and planned a sub- marine for sailing under the ice of the Arctic waters to the North Pole. It was realized that this way of traveling would save an explorer many tedious months and would in- crease the assurance of his reaching his destination. But the submarine was in its early stage of development and the carry- ing out of the plan never got much further than a few experiments. The extensive im- provements in the submarine since that time, however, have again brought this mat- ter up for serious consideration. The sub- marine required need not be very much dif- ferent from the Deutschland, it is said.