If the stimulus be not repeated, the synapses may be but temporary, and the memory fade as the group of cells is occupied by a new memory of some more potent sense stimulus. Many association tracts and synapses are laid down in the central nervous system when the child is born. These are the fruits of inheritance, and by their means, we may suppose, instinctive reflex actions are carried out. So long as the present stimuli are controlled by past memories and are active in recalling them, so long does consciousness exist, and the higher will be the consciousness, the greater the number and the more intense the character of the memories aroused. We may suppose that when all external stimuli are withdrawn, or the brain soothed by monotony of gentle repetition, and when the body is placed at rest, and the viscera are normal and give rise to no disturbing sensations, consciousness is then suspended, and natural sleep ensues. Either local fatigue of the muscles, or of the heart, or ennui, or exhaustion of some brain center usually leads us to seek those conditions in which sleep comes. The whole organism may sleep for the sake of the part. To avoid sleeplessness, we seek monotony of stimulus, either objective or subjective. In the latter case, we dwell on some monotonous memory picture, such as sheep passing one by one through a gap in the hedge. To obtain our object, we dismiss painful or exciting thoughts, keep the viscera in health, so that they may not force themselves upon our attention, and render the sense organs quiet by seeking darkness, silence and warmth.—L.H., in Nature. AMATEUR CHRONOPHOTOGRAPHIC APPARATUS. At the time that we described the Demeny chronophotographic apparatus we remarked that it had the advantage of permitting of the projection of very luminous images of large dimensions; but it is certain that the cases are somewhat limited in which there is any need of using a screen 24 or 25 feet square, and, as a general thing, one 6 or 10 feet square suffices. The manufacturer of the apparatus, M. Gaumont, has, therefore, been led to construct a small size in which the bands have the dimensions usually employed in the French and other apparatus, thus permitting of the use of such as are now found in abundance in the market. By reducing the size, it has been possible further to simplify the construction, and at the same time to reduce the price, thus making of the new form a genuine amateur apparatus. It will be remembered that the Demeny principle consists especially in the avoiding of traction upon the perforated part of the band, which is the portion that always presents the most fragility. This principle has naturally been preserved in the small model, and a preservation of the bands for a long time is thus assured. Fig. 1—ARRANGEMENT OF THE SENSITIZED BAND IN TWO MAGAZINES. Fig. 2—ARRANGEMENT FOR TAKING VIEWS WITH SPECIAL GEARING FOR THE WINDING OF THE BAND.