1884.] 



NEW YOKK ACADEMY OE SCIENCES. 



broad tread cylindrical wheels accurately ground. The central 

 pair are 32^% inches in diameter, and on the axle of these, a 

 worm of 1^ inch pitch, triplicate teeth, drives the worm 

 wlieel and shaft, having three universal joints and one slip joint, 

 which connects with and propels the mechanism of the recording 

 apparatus shown in Figs. I. and II. The truck carries many 

 distinct sets of special apparatus to furnish required indications, 

 tlie results being electrically recorded by the battery of electro- 

 magnetic pens on the rt-cording apparatus. 



Fie. I 



One-lwentieth of size. 



Fig. I. is a side elevation, and Fig. II. a top view of the re- 

 cordin^r apparatus. The instrument occupies a floor space of 

 about 34x4:0 inches, and is 37 inches high; projecting parts 

 extend a few inches outside of these dimensions. 



