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A Convenient La.boratory Device. 



By J. P. Naylor. 



For the last year we have been usi;ig a little device at Minshall Labo- 

 ratory that has proven serviceable in so many ways that it is thought that 

 it might be of sufficient interest to other members of the physics Section to 

 merit bringing it before you. Used in connection with the "Universal Sup- 

 ports," now so common in physical laboratories, the piece is so contrived 

 as to be adapted to a large number of experimental purposes. 



The apparatus consists of a four and one-half inch circle divided to 

 half degrees, and supported by a hollow spindle or axle. The spindle is 

 carried by a sleeve, about three inches long, having at one end a strong 

 crossbar. This crossbar is fitted at one end with a vernier reading on the 

 divided circle to three minutes of arc and at the other end with a slow 

 motion screw and clamp arranged to act upon the circle. The hole 

 through the spindle will take a ten millimeter rod which can be clamped, 

 by means of a screw, at any desired point. To this rod are attached the 

 various pieces that make it possible to use the device in so many different 

 ways. In fact, it is in the hollow spindle that the adaptability and genera! 

 usefulness of the apparatus lies. 



Perhaps merely mentioning a few of the purposes for which it can be 

 used will best suggest its adaptability in laboratory or investigation work. 

 It can be used for measuring tlie torsion of wires by twisting, for the 

 torsion head of an electro-dynamometer, for measuring the indices of refrac- 

 tion of plane parallel plates, for measuring the angles of prisms, for mak- 

 ing up a Kohlrausch total-reflectometer, for measuring the indices of 

 liquids by Wallaston's method, for arranging a Wallaston's goniometer, 

 for making up a simple polariscope or sacharimeter, as a support for meas- 

 uring the angular aperture of a microscope objective or photograph lens, 

 and for many other purposes. In fact, the apparatus can be used in a 

 large majority of cases where the measurement of an angle is an essential 

 part of the work. The figure shows the use of the apparatus in making up 

 a Kohlrausch total-reflectometer. 



