350 Proceedings of the Royal Flvysical Society. 



have in all fourteen available variations of rate for smoked 

 work. These vary from one revolution in 8 seconds to one 

 revolution in 12 minutes. Were further differences of rate 

 required, they could be obtained by increasing the complexity 

 of the pulleys, but it seems to me that the arrangement de- 

 scribed is ample for all purposes. 



The motion is exceedingly steady, and the stand can be 

 readily moved on the table so as to adapt it to the recorders, 

 it being only necessary to see that the band is kept reasonably 

 tight. Further, by setting the clock on its end and the stand 

 on its upright, the drum can be made to rotate in a horizontal 

 position. The direction of rotation can also be readily reversed, 

 when vertical or horizontal, by twisting the cord on itself. 



2. Apparatus for Co^^tinuous Paper. 



The Cambridge Scientific Instrument Company supply, at 

 a cheap rate, recording paper in long rolls and of any 

 breadth. Each of these rolls is provided with a wooden core 

 2 in. in diameter, and pierced by a hole about J in. in dia- 

 meter. Such a roll is fitted on a brass bobbin, the details of 

 which are seen in PL XIV., Fig. 2. The bobbin consists of a 

 brass tube a little shorter than the core, and fitting it tightly. 

 This tube is screwed into a hole in a circular brass plate 8 

 in. in diameter. The whole is set in an upright iron stand 

 of such a thickness as will permit the tube to turn on it 

 readily. The height of the bobbin is regulated by a collar, 

 which can be clamped at any height on the stand. On the 

 top of the core rests a disc, the central portion of which is 

 thicker than the peripheral. The central portion is 1^ in. in 

 diameter, and bears on the core, the thinner part projecting 

 a little over the paper, but not touching it. A bow-shaped 

 spring made of flat steel rests on the disc, and can be forced 

 down so as to press the disc on to the core. A clamp keeps 

 the spring in position. By this means the resistance ot the 

 web to its being unwound can be increased or diminished. 

 The end of the paper passes round the drum on the wooden 

 stand already described, which acts as a recording surface, 

 and near which the paper bobbin is placed. From this the 

 paper passes on to a brass bobbin, which is now set on the 



