On some Modifications of Recording Ajyparatns. 351 



clockwork in precisely the same way as was the drum in 

 PL XII. This bobbin is 6^ in. in length, 3 in. in diameter, 

 and a flange at its lower end projects 2 in. all round. 

 There is also a narrow flange at the top. The end of the 

 paper is attached to this bobbin by a little gum, and on the 

 clock being started the paper is wound on to the bobbin, 

 passing in a steady fashion over the drum, which turns with 

 it, and forms an excellent recording surface. 



This simple arrangement, by which the paper is wound up 

 as it passes the pens, instead of running out on the table or 

 floor as it does in some other forms of continuous apparatus, 

 is, I take it, a considerable advantage. In the latter case the 

 paper gets much in the way, and is apt to be torn when it 

 comes to be rolled up or examined, the coils frequently 

 getting mixed up. The only objection to the system that I 

 can conceive is, that the rate of motion past the recorders 

 will increase slightly as the bobbin gets filled, but this is of 

 course readily checked by the time markers. Should it be 

 desired, however, to have the paper running out without 

 being wound up, a pair of friction rollers can be pressed on 

 to the bobbin, and the paper run out in the ordinary way. 

 The attachments for these rollers are seen to the left upright 

 on the clock frame, PL XIII. 



When the paper is to be removed from the bobbin, the 

 web is cut through, the clock turned on its end, and the pin 

 withdrawn from the lower end of the spindle. In this way 

 the paper can be unwound and rolled or folded into lengths 

 as may be convenient. 



The entire apparatus can be made by Messrs H. & J. 



Millar, clockmakers, Castle Bank Works, for something under 



£10. 



3. Time Maeker. 



When long tracings are being taken, the attention de- 

 manded in order to keep the pens supplied with ink is often 

 considerable. With the view of reducing this somewhat, I 

 venture to describe an arrangement of time-marking pens 

 which I have found exceedingly convenient. 



The idea is a modification of the neat time-marker of the 

 Cambridge Scientific Instrument Company, and is, I believe, 



