A New Angle Measurer. 



197 



A NEW ANGLE MEASURES. 



BY THE KEY. N. J. HEINEKEN. 



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his instrument,, which I have lately contrived, is on the 

 principle of Schmalcalder's quadrant, but of dimensions small 

 enough for the waistcoat pocket. In the Schmalcalder, more- 

 over, a prism is used for reading off the angle at the same 

 time that the object is viewed. In mine, the divisions are 

 read off by a lens, and a needle point, passing through the side 

 of the tube, and close to the divided wheel, forms the index. 

 The object is seen with the other eye at the same time ; the 

 instrument being elevated or depressed, till the needle point 

 appears to be in contact with the object as well as with the 

 division of the circle. The angle of altitude is thus indicated. 

 The drawings are of full size. I add a description and measure- 

 ments of the instrument. A flanged wheel 1-^ inch diameter, 

 has one half and a little more divided into degrees, the sur- 

 plus being for index error ; edge of wheel -^ wide ; flange on 

 each side about -y^-deep. Within this flange on one side is a 

 large-headed screw of brass, and on the opposite side a trian- 

 gular piece of copper to which it is attached. The screw 

 passes through a slotted hole in the wheel. The screw and 

 piece of copper form a counterpoise to the wheel, and the 

 slot allows of adjustment of the Zero point. 



A brass tube 2-?-^ long and -^ diameter is filed out at one 

 end so as to admit the above wheel, which is suspended as 

 delicately as possible by a fine pointed screw on each side, the 

 points of which screws enter a very fine hole, drilled in the axis 

 of the wheel ; upon the nicety of this suspension the accuracy 

 of the instrument depends. 



An aperture is made in the tube, near the wheel, to admit 

 light for reading off the divisions, and moreover at this part 

 the interior of the tube is silvered. 



