Jan. 14, I 



NATURE 



249 



side view of the shafting, to which a number of pulleys are 

 fixed. One of these, e, drives a second pulley, F, which 

 is supported by a frame turning about a pivot, G. The 

 pulley F has three grooves in it. A short leather band 

 passes round the centre groove and round the pulley E ; 

 thus, if the centres of the pulleys E and F are brought 

 together, the leather band which receives its motion from 

 E will slip round F without driving it ; but on the other 

 hand, if the centres are pulled apart, f will be driven. 

 When the cord h is pulled, the centres are brought toge- 

 ther, and when released, a weight, K, gives the necessary 



S 



tension to the leather band. The endless cord L, which 

 conveys power to one of the various rooms, is driven 

 by the pulley F. This arrangement is something like 

 that adopted for connecting the fly-wheel of the gas- 

 engine with the shafting. The cord L first passes three- 

 quarters of a turn round one of the grooves in the pulley 

 F, under the pulley, m, which supports the weight k, and 

 a quarter of a turn round the other groove of the pulley 

 F. The cord then passes away in a horizontal direction, 

 and is guided by pulleys round angles, either in a vertical 

 or horizontal plane, to the rooms where the power is 



required. It is then guided in the same manner along 

 the edge of each of the tables on which the instruments 

 are to stand. The weight k, besides giving the neces- 

 sary tension to the leather band, will take up all slack in 

 the cord L. The cord runs near the ceiling, and is either led 

 over pulleys and down to the tables in the rooms, or up 

 through the ceiling to tables standing on the floor above. 

 The power is transmitted as follows to the instruments 

 standing on the table from the cord running along its 

 edge. Fig. 3 shows a piece of apparatus designed for 

 this purpose, which has been called a driving-pulley. It 

 is clamped to the edge of the table, and the cord is then 

 made to pass round the pulley, P, as shown. This has the 

 eft'ect of raising the weight k. Fig. 2. The instruments are 

 driven by a light cotton band passing round one of two 

 grooves in a pulley fixed to the same spindle as the 

 pulley P. The larger of the grooves is shown at Q, the 

 smaller is not visible in the figure. The band is kept 

 tight by means of a pulley and a weight, in the manner 

 previously described ; this arrangement also allows the 



instrument to be moved to any distance from the driving 

 pulley without altering" the length of the band. 



In the figure, the instrument being driven is shown at R. 

 It is essential that it may be stopped without interfering 

 with the cord which supplies power to the room. This is 

 done in the following manner, which we believe is new. 

 The handle T is fixed to a brass piece formed in the 

 shape of a sector of a pulley, with an o\erhanging edge. 

 It is arranged to turn about the bearing through which 

 the spindle of the pulley Q passes, and can therefore 

 rotate about the same axis as this pulley. The groove in 

 the overhanging edge is in a line with the groove in the 

 pulley. In the figure the cotton band is shown resting in 

 this groove, and not in the groove of the pulley Q ; now, 

 if the sector is turned through half a revolution by the 

 handle T, the cotton band will fall from it into the groove 

 in the pulley Q. Thus the instrument is started ; the 

 reverse action not only throws it out of gear, but the 

 friction of the cord running in the groove in the sector 

 acts as a brake, and brings it quickly to rest. From the 



