automatic record of growth 9 



Automatic Record of the Rate of Growth 



Another obstacle to obtaining an accurate record of the 

 curve of growth arises from the friction of contact of the 

 bent tip of the writing lever with the recording smoked 

 surface of glass. This difficulty was removed by an oscillat- 

 ing device (fig. 2) ; the smoked glass plate G is made to 

 oscillate, to and fro, at right angles to the tip of the writing 

 lever ; the oscillations are at regular intervals, say once 

 in a second. The bent tip of the writer thus comes 

 periodically into contact with the recording plate during its 

 extreme forward movement. The record of growth there- 

 fore consists of a series of dots, the distance between them 

 representing magnified growth during a second. 



The approach of the recording surface to the writing 

 lever has to be rendered very gradual, otherwise the sudden 

 stroke of the plate causes an after-oscillation of the WTiting 

 lever, resulting in multiple dots which spoil the record. 

 In order to obviate this, a special contrivance had to be 

 devised by which the speed of approach of the plate was 

 gradually reduced to zero on contact with the writer ; 

 the rate of recession should, on the other hand, continuously 

 increase from zero to maximum. The writer will in this 

 manner be gently pressed against the glass plate, marking 

 the dot, and then set free. It is only by strict observance 

 of these conditions that the disturbing effect of after- 

 vibration of the lever can be obviated. 



The oscillating device consists of an eccentric E, a crank 

 K actuated by clockwork, and a slide S, supported on ball- 

 bearings, which carries the smoked glass plate. The 

 eccentric consists of a cylindrical rod of glass mounted 

 eccentrically. A semi-rotation of the eccentric in one 

 direction pushes the recording plate gradually forwards, 

 while that in the opposite direction causes it to recede 

 (fig. 2). The eccentric is actuated by the crank K, which 

 in its turn is acted on bv clockwork which releases a re- 

 volving wheel at intervals of i, 2, 10 or 15 seconds, according 



