200 



Plain Polar Planimeter. 



This Planimeter is of German silver, with adjustable tracer arm fully gradu- 

 ated, about 9 inches long, in polished mahogany box with proving liar. 



Pric6 of instrument when rated as explained on page 82 . . s.'Jl.OO 



" " " not rated but with all the improvements . "27.00 



Precision Plaiiimeters. 



These Planimeters are very much more accurate than the ordinary Polar 1'lani- 

 meters. The graduated rollers do not touch the paper at all, but roll, instead, on a 

 hard, highly polished surface of steel, thus eliminating all errors due to the inv-u- 

 larities of the paper surface. 



No. 1O9. Large Suspended Ball Planimeter. 



Not kept in stock. 



This instrument is capable of doing very accurate work. The tracer arm is llf 

 inches long, the pole arm is 6 inches long, and the diameter of the toothed circle on 

 the pole is 6 inches. The angular motion of the tracer arm is about i)0. 



Surfaces from 2 x4 inches to 7 x 10 inches can be measured without moving the 

 pole. 



Price of instrument complete packed in morocco box . . . $75.00 



No. 11O. Large Rolling Ball Planimeter. 



u Th f Planimeter illustrated above is made of German silver and ^^^ 



bronzed brass, and enables to obtain results of greater accuracy than ^V 



any other Planimeter vet made, both on large and small surfaces. The ^ 



tracer arm is graduated throughout and has a length of 12 inches which can 

 be increased by a lengthener to 22 inches. Its angular motion is about qo. 

 I he two rollers are made of exactly equal diameters, ensuring a motion of the 

 instrument, as a whole, in a straight line. A surface of any length and a width of 

 2o inches can be measured with the 22 inch tracer arm. 



Price of instrument, with testing liar enabling to check areas 

 of known radii, and table of settings, in velvet -lined morocco box 

 lock 



$85.OO 



