October 26, 1917] 



SCIENCE 



417 



The central part of the tripod base is bored 

 and faced on the lathe, and the hole is reamed 

 to a standard size. The base is then placed 

 on an arbor and the lower surface of the hub 

 is turned to correspond with the front. The 

 lower end of the vertical rod is ground into 

 the hole. A collar is securely fastened to this 

 part of the rod, and its lower surface turned 

 to an accurate bearing. A long rod is screwed 

 into the collar, and is firmly pressed against 

 the adjusting screw F by the steel rod A, 

 which acts as a very strong spring. The 

 vertical rod is fastened to the base by a screw 

 in its lower end, and a spring washer which 

 bears against the turned surface. As the 

 horizontal rod has a considerable length, and 

 the adjusting screw a fine thread, the rotation 

 of the rod when the screw is turned is very 

 slow, and is under perfect control. The elas- 

 ticity of the spring rod is sufficient to allow 



the necessary movement in graphic experi- 

 ments, and is rigid enough to prevent rotation 

 when the stand is used for ordinary purposes. 



The vertical rod of the stand just described 

 has a diameter of 10 mm. A much larger 

 stand of slightly modified construction, with 

 a heavy base, and a rod 25 mm. in diameter, 

 is a most useful addition to the equipment of 

 the laboratory, and forms a very satisfactory 

 support for a reading telescope. The lower 

 end of the rod is turned to a shoulder, and is 

 fitted to the base with a screw and a washer, 

 as in the previously described instrument. 

 The collar into which the horizontal arm is 

 inserted is not permanently fastened to the 

 central rod, but is clamped by a thumb-screw 

 which permits the rod to be rotated to any 

 extent before using the fine adjustment. A 

 leveling-screw, and a clamp-screw in the hub 

 not shown in the figure are also desirable 

 additions. 



Universal Clamps. — The clamps shown in 

 the drawing were designed to be used on the 

 adjustable stand. Within the limits of their 

 capacity they enable flat objects, and rods of 

 round, square, triangular and oblong section, 

 to be held very firmly in any position without 

 marring. They can be easily adapted to any 

 stand and modified in various ways. The 

 clamps are attached to the supporting rod by 

 a split east-iron piece in the shape of two 

 crossed cylinders, which are carefully bored 

 at right angles to each other. The bolt which 

 passes through the horizontal cylinder has the 

 same size as the vertical rod, and in one form 

 has for the head the iron disc J, which is per- 

 manently fastened to it. A similar disc re- 

 volving on the bolt, forms the second jaw. 

 The two discs are turned, and their inner sur- 

 faces have parallel Y grooves which accurately 

 correspond, and a recess in each for a spiral 

 spring which opens the jaws when the nut is 

 loosened. The object to be held is fixed in 

 the jaws, and the clamp to the stand by the 

 single nut N. 



The upper clamp is fixed to the vertical 

 rod independently by the lever L which turns 

 a screw in the split projection. The bolt W 

 has a number of transverse holes which enable 



