900 SEC. 20. COLLECTION OF APPARATUS AND PHOTOGRAPHS 



II., III., IV. Galvanic chronographic interrupter, described in the Nuovo 

 Cimento, t. xii., p. 115, and t. xiii., p. 266*. It opens and shuts successively 

 electric circuits, measuring the intervals of time by the diapason (d), which by 

 vibration marks by a stile the oscillations on the smoked cylinder (c). 

 Perpendicular to the axis of the cylinder are eight rays, which rotate with it, and 

 are furnished with small stops of steel isolated on ebonite. These, striking 

 on the levers (7)> detach them from the pieces (p) opening and closing 

 the circuits, since a mechanical method of closing reduces itself to one of 

 opening. For the ordinary way of closing, the piece (#) is used, which is to 

 be found on fol. iii. (see description quoted). The surfaces of contact at the 

 points of interruption are of silver, and to make them fit better the 

 cylinders (p) are movable on their own axis. The diapason is movable 

 around a horizontal axis (fol. iv.), and can slide along it. The plate which 

 carries it is movable round a vertical axis ; the correcting screw h can incline it 

 slightly. The screw z regulates the contact of the stile with the cylinder. 

 The piece a, which turns with the cylinder, at one point of the experiment 

 meets the piece b lifting the diapason. The small bit of wood s serves to set 

 the diapason in vibration. The base of the apparatus is of cast zinc, 

 length - 64, breadth 0*19 meter. The remainder is of brass, except the 

 isolating pieces, which are of ebonite. 



4571. Drawing of Two Sections of the Carnic and 



Julian Alps. (One plate, m. 80 by m. 40.) 



Technical School at Udine ; Director, Torguato Taramelli, 

 Professor of Physical and Natural Science. 



COLLECTION CONTRIBUTED BY THE RE ALE ISTI- 

 TUTO DI STUDII SUPERIORI PRATICI E DI 

 PERFEZIONAMENTO, FLORENCE. PRESIDENT 

 COMMENDATORE SIGNOR PERUZZI. 



INSTRUMENTS OF GALILEO. 



Galileo's Telescope. Object glass, 50 mm. in diameter ; 

 eye-glass, plano-concave, 23 mm. in diameter, It served for the most 

 important discoveries and experiments of Galileo, and was con- 

 structed by himself. 



Galileo's Telescope. Object glass, 38 mm. in diameter ; 

 eye-glass, double concave, 19 mm. in diameter; made by Galileo. 



Object Glass of the diameter of 40 mm., made by Galileo, 



and with which he discovered the satellites of Jupiter on the 9th 



* In the apparatus described in the Nuovo Cimento there is a Froment's 

 Siren instead of the diapason, the piece a is wanting, and there are only two 

 radii r. 



