In concluding, we will remark that, without employing springs, we may increase the aperture of the shutter without varying the time of exposure. To effect this it is only necessary to raise the point of the shutter's drop. In fact, as may be seen in Fig. 4, all the vibrations of the stylet corresponding to 1/100 of a second always continue to elongate, and it will consequently be possible for the same time of exposure to considerably increase the aperture and, as a consequence, the effective time, by causing the guillotine to drop from a greater elevation. From this study, which has principally concerned the guillotine shutter, can we draw the deduction that this type of apparatus will become a definite one? We think not. In fact, along with its decided advantages the guillotine has a few defects that cannot be passed over in silence. The aperture, in measure as it is increased, renders the apparatus delicate and subject to become bent. If, in order to obviate this trouble, we employ plates of steels, we increase its weight considerably, and the chamber becomes subject to vibration at the moment the shutter drops. If rubber or springs are used for increasing the velocity, it is still worse. Moreover, it is quite difficult to obtain a graduation, and to our knowledge, and probably for this reason, it has not yet been applied. The reader will please excuse us for this perhaps somewhat dry theoretical _expose_, but we have thought it well to give it in the hope that it might well show the qualities that should be required of a photographic shutter and particularly of the guillotine. Moreover, at the point to which photography has arrived it is no longer permitted to do things by halves. After the memorable discoveries of Nicephore, Niepce, Daguerre, and Talbot, photography remained for some time stationary, limited to the production of portraits and landscapes. But for a few years past it has taken a new impetus, and new processes have come to the surface. In the graphic arts and in the sciences it has taken considerable place. Being the daughter of chemistry and physics, it is not astonishing that we require of it the precision of both. It is, moreover, through a profound study of the reactions that gave it birth and through a knowledge of the laws of optics that it has come into current use in laboratories. In fact, it alone is capable of giving with an undoubted character of truthfulness a durable vestige of certain fleeting phenomena.-- _A. Londe, in La Nature_. * * * * * FALCONETTI'S CONTINUOUSLY PRIMED SIPHON.