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SCIENCE— ADVERTISEMENTS 



THIS new form of Demonstration Balance enables the most accurate verifica- 

 tion of the principles of moments. The adjustments permit of varying the 

 conditions in the greatest number of ways. The center of gravity may be 

 changed so as to be either below, on the level with, or above the knife edge. 

 The knife edge itself is a very delicate construction and is made by allowing two 

 very hard steel points to rest in two V shaped grooves. The counterweight on 

 the pointer permits of adjusting its weight. The plumb bobs on the scale pans 

 and support permit of accurately leveling this apparatus and make it possible to 

 make the forces act in the exact perpendicular to the length of the lever arm. 

 The scale and a clamp which holds the knife edge are both adjustable and the 

 entire is mounted on a tripod base with leveling screws. Nickel plated through- 

 out, making a very handsome appearance. 



W. M. WELCH SCIENTIFIC COMPANY 



Manufacturers, Importers and Exporters of Scientific Apparatus 

 1516 Orleans Street CHICAGO, ILL., U. S. A. 



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