360 Locke 



triangulat outline, with the armatures fastened across their apices. The 

 triangular shape not only produces on flexion a rapidly increasing resistance 

 to further flexion, which prevents an armature being brought in contact 

 with a pole, but also makes its movement very much more dead-beat, 

 owing to interference in their tendency to vibration of the longitudinal 

 elements of different lengths. 



(2) The screw adjustment of the strength of the armature-springs and 

 the distances of the armatures from the poles. The screws act indirectly 

 on the armature-springs through two accessory springs of sheet phosphor- 

 bronze, the mode of action of which is obvious in the figure. These, besides 

 producing a very smooth and gradual adjustment, increase further the 

 dead-beatness of the armatures in the case of downward movements. 



Fig. 1. — Double signal. | real size. The "legs" of the suspension of the writing- 

 lever are a little longer than usual for the sake of greater clearness. 



(3) The armatures and pole-pieces are of special construction, the latter 

 being conical in shape, and the armatures stamped out conically to fit over 

 them. Magnetic attraction is thus made to take place through a longer 

 range, with a strength less rapidly increasing with approximation of the 

 armature than with the usual arrangement. 



(4) The suspension of the writing-lever between the two armatures 

 consists of two spirals, one right- and the other left-handed, of thin German- 

 silver, brass, or platinoid wire, which fit into one another with their coils 

 alternating to form a tubular socket 1'2-1'4 mm. in diameter and 4 min. 

 long, for the writing-lever. The ends of the two spirals make four legs 

 and feet, so to speak, a pair of feet being attached to each armature by 

 the same screws which attach it to its spring, and form a flexure joint 

 permitting sufficient freedom of movement without the complicated con- 

 struction and other disadvantages of friction-joints. 



(5) In the double-spiral socket a writing-lever about 5 cm. long of 



