326 MR. A. E. TDTTON ON A COMPENSATED INTERFERENCE DILATOMETER. 



from and forming part of the bearing casting, and which presses upwards on rotation 

 against a V-piece attached to the optical tube. Two such V-pieces are provided, on 

 the under and upper sides of the tube. It is convenient to have a means of recording 

 the proper tilt of the telescope corresponding to the adjustment of each of the 

 spectral lines (and therefore of the corresponding signal images and interference 



Fig. 5. 



bands), whose light is to be employed in the observations. This is delicately 

 achieved by placing a sharp edged flange above the milled head of the tilting screw 

 and employing it as the indicator of a vertical scale, divided on silver to half milli- 

 metres, and suspended from the horizontal arm which carries the screw. 



The method of suspension is by a slider whose rectangular aperture is slightly larger 



