for resolving Transcendental Equations. 427 



carried round, bodily, by the attachment of its center to the end 

 of a revolving arm, whose length may either be permanent or 

 adjustable by a slider. Hence arose the following construction 

 which seems to be as simple as the nature of the problem 

 admits. 



(3.) In figure 1, C is a horizontal axis at right angles to the 

 plane of the paper, on which is firmly fixed at right angles, or in 

 the plane of rotation of the axis, a cross piece, having a bevelled 

 groove PQ, in which the slider SR moves freely backwards and 

 forwards until arrested and fastened by a clamping screw. Pro- 

 jecting forwards from the slider SR, and firmly rivetted into it is 

 a short pin B, on which, as on an axis, the excentric wheel DEF 

 is set, and permitted to turn freely until also arrested and clamped. 

 These clampings are both easily performed by means of a male 

 screw cut on the end of the pin B on which is fitted a female 

 screw cut in the cross head, or clamping hey mn. When this screw 

 is loosened the slider SR can move in its groove and the wheel 

 DEF revolve on the pin B, but when tightened these motions 

 are rendered impossible, and the whole apparatus, cross-piece, 

 slider, and excentric wheel become part of the axis C, and revolve 

 with it as one mass. Thus we are enabled to adjust, first, the 

 distance of the center B from the axis, and secondly, the position 

 of a given point in the circumference of the excentric wheel with 

 respect to a horizontal line. 



(4) The axis C also carries an index-arm CH furnished either 

 with a simple index like a clock's hand, or if accuracy be re- 

 quired with a vernier adapted to subdivide the graduations of an 

 index-circle AH concentric with C, and divided into degrees, &c. 

 Around the excentric wheel DEF a thread of some fine and in- 

 extensible material (such as dentist's silk or very delicate silver 

 wire) is wound. For this purpose the edge of the excentric wheel 



Vol. IV. Part III. 3 I 



