THE NEW ACME STAND. 87 



the family circle, and objects can thus be exhibited 

 with great rapidity. 



By means of a strong trunnion joint the body of the 

 instrument can be inclined at any desired position 

 between the vertical and horizontal, the requisite 

 stability of motion being secured by heavy " cheek- 

 blocks;" the joint has also compensation for wear. 



All the working part of the Acme above the base are 

 of solid brass, bright finished, and nicely lacquered. 



The main body-tube- is one and five-sixteenth inches 

 in diameter. This tube articulates with the limb by 

 means of heavy "T" guides or angle pieces, thus secur- 

 ing broad bearing surfaces and also perfect freedom 

 from lateral displacement. Mr. Sidle has put himself 

 to much trouble to perfect this portion of the stand. 



The main-tube is five inches in length. This is sup- 

 plemented with a draw-tube, which can be drawn out 

 to the standard length of ten inches when desired. 



The coarse adjustment is by rack and pinion. The 

 rack is well cut and durable, and the movement of the 

 tube by means of operating the large milled heads is 

 exceedingly smooth and entirely without "lost motion." 



The fine adjustment is by a large milled head place 

 at the rear of the limb, and operating the main tube. 

 This milled head is one and one-fourth inches in diam- 

 eter, and is divided into twenty divisions. It acts 

 directly, i. e., without lever, on a micrometer screw 

 cut fifty threads to the inch, each division of the milled 

 head representing one one-thousandth of an inch. The 

 fine adjustment can therefore be easily made to answer 



