EXPERIMENTS ON THE FROUDE. 113 
fied in the ratio of about 9 to 1 was transmitted directly to the tape by 
means of a very fine wire attached to the carriage holding the pen. ‘This 
carriage consisted of a rod which carried the pen socket, S,, and which rested 
on pin-bearing pulleys P at each side of the table T (see Fig. 30). These 
permitted a very free movement across the table. As the spring deflected, 
the carriage traveled across the paper at right angles to its line of motion 
and traced a curve thereon; the heighth of which gave a measure of the 
thrust to be added to that taken up by scale beam weight. ‘The scale for 
this curve was about 25 pounds to the inch. 
DD is the record of the thrust pen drawn from EE as a base line by 
a pen in the socket S,. The line base was drawn by the pen in S2 and was 
adjusted to agree with the zero deflection of the spring. The zero was 
tested between each run by pushing the scale beam lever down until it 
was out of contact with the spring. 
Fountain pens of special construction were used for all the records and 
they worked perfectly, on several instances when the apparatus was used 
on progressive speed trials they drew continuous lines for about eight hours. 
