weight, x'. By the falling ball this arm is pressed downward, and the lower horizontal arm, w, of the lever is also moved. On a second horizontal axis the lever, v, partly concealed, moves, restricted as to its length of swing by the screws, n. As long as the concealed arm is not moved, v is lightly pressed by the small spring, e, against w. The projection, z, at the upper end of v holds the rod, i, which the strong spring, h, is continually pressing upward. When the ball falls upon the plate, p, the arm, w, presses against the lower end of v, the projection, z, sets free the rod, and it springs upward. This movement is soon arrested, as the projection, z', engages with a stud situated on the right side of the rod, i. This projection is situated on the vertical arm of an angular lever whose other arm is the key, t. When the observer presses the key, the rod, i, again is jerked upward by the spring, h. The screw, o, tapped into the rod, i, prevents the rod going higher than necessary, by striking a plate, which also serves as guide for i.

To determine the interval between the falling of the ball and pressing of the key, one has finally to count the waves inscribed by the tuning fork, which come under the portion of the line inscribed by s, which is bounded by the two breaks produced by the successive movements of the rod.

To make the glass plate carried by the frame available for more observations, which plate can be used as a photographic negative, the frame, T, is adjustable up and down upon the pillars, N. This frame carries the tuning fork, mercury cup, n, and the electro-magnet, M. The spring, s, can also be moved up and down along the rod, i.—H. Heele in Zeitschrift fur Instrumentenkunde.

A NEW DISINFECTOR.

The accompanying engravings represent a new disinfecting apparatus invented by Mr. W.E. Thursfield, M. Inst. C.E., of Victorgasse, Vienna. The principle on which its action is based is that the complete destruction of all germs in wearing apparel and bedding, without any material injury whatever to the latter, is only to be obtained by subjecting the articles infected, for a period proportionate to their structural resistance, to a moist heat of at least 212 deg. Fah. Recent experiences in Berlin have shown that, for security's sake, a temperature of 220 deg. is better. To insure the thorough penetration of this temperature in every fiber, a heat of from 260 deg. to 270 deg. must be maintained in the disinfecting chamber itself. To obtain this by means of ordinary or superheated steam involves the employment of boilers working under a pressure of 2½ to 3 atmospheres, of disinfecting chambers capable of resisting an equal tension, and of skilled labor in attending to the same; in other words, a large initial outlay and correspondingly heavy working expenses in fuel and wages.