UNWIN S AUTOGRAPHIC APPARATUS. 



229 



the simultaneous movement of the weight, this distance 

 moved by the pencil will be a measure of the load upon the 

 specimen, to a certain scale. This is the plan which is 

 adopted in all instruments of the present class. 



Among these are the instrument of Professor Unwin, 

 and a number of others very similar in principle, such as 

 those of Mr. Aspinall, Professor Hele-Shaw, and Professor 

 Hearson ; there are also a number of Continental and 

 American designs based essentially on the same principles. 



FIG. 108. Diagrammatic Sketch of Unwin's Autographic Apparatus. 



127. Professor Unwin's Autographic Apparatus.* The 



general scheme of this instrument is given on the diagram 

 on Fig. 108. Here, the specimen which is being tested is 

 marked S, and the rotating drum which carries the paper 

 upon which the diagram is to be drawn is shown at B. It 

 will be seen that the drum is placed in a vertical position, 

 and rotates on a spindle which terminates in a worm wheel 

 at D. Upon the drum is fixed a sheet of paper, and the 



* See Unwin's ''Testing," p. 236. 



