CENTRAL SCIENTIFIC CO., CHICAGO, TJ. S. A. 



616. BALANCE, Specific Gravity, Jolly's Spiral Spring, improved design. The 

 upright is nickel-plated, 100 centimeters long, graduated in millimeters, 

 and supported by a heavy japanned iron tripod base, fitted with leveling 

 screws. The support for the spring is adjustable and can be inverted for 

 light loads or heavier springs. As the upright rod is graduated for its full 

 length this spring support may be set at any given point, and may be 

 moved during an experiment provided the amount of its motion is added 

 to or subtracted from the stretch of the spring. The indicator at the end 

 of the spring may thus be kept at a convenient height during an entire 

 experiment. 



Attached to the sliding index is a small mirror with a horizontal line etched 

 upon it, and a device for limiting the motion of the spring. The indicator 

 attached to the end of the spring is a small metal disc which may be set 

 very accurately in line with its own image and the etched line on the 

 glass. The position of the index is then read directly from the scale. This 

 method of reading embodies all the advantages of the mirror scale, and 

 at the same time does away with the necessity of reading the position of 

 the index while attempting to hold three objects in line with the eye. 



The platform for holding the beaker of water or other liquid is of oxidized 

 brass and slides on the upright, to which it can be clamped in any posi- 

 tion. For experiments in cohesion or surface tension a device is provided 

 by which the platform may be fastened to and moved with the sliding 

 index. The lower pan is of glass suspended by fine 

 platinum wires. The springs are of the best steel, 

 conical in form, especially made for Jolly Balance 

 work. Two springs, one high and one low tension, 

 are supplied with the balance $17.50 



No. 616. 



018. BALANCE, Specific Gravity, Jolly's Spiral Spring, made entirely of metal 

 and nicely finished throughout. The upright is a nickel plated rod 100 cm 

 long supported by a japanned iron tripod base. The platform is of oxidized 

 brass which slides along the rod and can be clamped in any position. The 

 spring support is also adjustable and can be inverted for light loads or 

 heavier springs, allowing a larger range. An adjustable mirror scale 65 cm 

 long, graduated in millimeters, is provided. The pans are of aluminum. 

 Furnished complete with spring No. 628 5.50 



620. SCALE PAN, for Jolly's Spiral Spring Balance. Lower pan of aluminum, 

 with copper wires .25 



622. SCALE PAN, for Jolly's Spiral Spring Balance. Upper pan of aluminum, 

 with copper wires .25 



624. SCALE PAN, for Jolly's Spiral Spring Balance. Lower pan of glass, with 

 platinum wires .75 



No. 618. 



626. SPRING for Jolly's Balance, light. . 

 628. SPUING for Jolly's Balance, heavy. 



.45 

 .45 



