199 



For the ronrenience of our customers we append a list of miscellaneous articles kept ir 

 stock, but must of them are not of our manufacture. Those not made by us are of the boat 

 quality obtainable, and the price* quoted are identical with those in the market. 



Precision Pantographs. 



The arms of these Panto- /-^a&arfP'^HfC graphs, to avoid friction on the paper, are suspended 

 from a solid iron support (as will %g^Ff(j9? jl|@ be seen in cut), the latier being supplied with levels 

 and leveling screws. The instru- / ' ment is capable of enlarging or reducing in all ratios, 



and is very useful for copying. The brass arms are hollow and square in cross- 



section, and are divided to millimeters with verniers reading to ^j mm. For the accurate setting of the 

 verniers slow motion screws are provided. All swivel joints turn upon center points. The disengaging mech- 

 anism is a special convenience. The ratios from J to Ar are set with pole at end, those from ij to i to f 

 are set in the middle. The pole'and pencil-holder are therefore interchangeable. 



No. 99. Suspended Pantograph, arms about 24 inches long, in wooden case. 



Price, as above, $15O.OO. 

 No. 100. Suspended Pantograph, arms about 38 inches loner, in wooden case. 



Price, as above $18O.OO. 



NOTE The Pantograph with 24-inch arms when set at 3 can circumsciibe a io-inch square, or an 

 oblong 155 x 24 inches, approximately. 



The Pantograph with 38-inch arms can circumscribe a si-itch square, or an oblong 27^ x 39 inches, 

 approximately. 



Compensation Planimeter. 



See pages 82 and 83. 



The compensation Planimeter illustrated above consists of two parts, which pack separately in the case, 

 the tracing frame and the pole arm. The tiacing frame rests on 3 points, the measuring wheel, the tracer 

 point and the roller. A finely polished steel ball, fixed at one end of the pole arm, rests in an opening of the 

 tracer arm, forming a ball and socket joint. This joint forms the axis of rotation ot the tracer arm, which by 

 means of the pole arm moves on a circle as guide line ; at the same time it enables the tracing frame always to 

 rest with its three points on the plan. The length of tracer arm is about 9 1-2 inches and pole arm 7 1-2 inches. 



The pole consists of a brass cylinder attached at one end of the pole arm. Its lower surface forms an 

 edge at right angles to the pole arm, which by the rocking motion provided by this edge can be lowered until 

 its other end, which carries the ball, is firmly secured in the socket. In the center of this brass cylinder a 

 small steel pin is inserted and kept in place by a set screw. This pin terminates at both tnds in a finely 

 hardened point, one of which projects slightly under the lower edge of the cylinder. The tracer arm is pro- 

 vided with a vernier and micrometer screw by which it can be placed at any division mark on the tracer arm, 

 which is graduated throughout in 1-2 mm. The axle of the measuring wheel, ending in finely made pivots, is 

 of the best hardened steel working in cylindrical steel point bearings. With t! e Planimeter is supplied a 

 proving bar, which enables by its graduations to describe several circles of known radii. 



In using, place the Planimeter approximately in the center of the area to be measured, so that the plane of 

 the measuring wheel, if extended, passes through the pole. After obtaining the measurement by using the 

 Planimeter with the pole arm on one side of the tracer arm, the pole arm may be placed on the other side and 

 another measurement made. The mean of these two readings will eliminate any error of the measuring wheel, 

 thus this form of instrument is a compensation Planimeter. 



If the area to be measured is too large for the scope of the instrument it should be subdivided into smaller 

 areas. According to the importance of results to be obtained, one measurement may be sufficient around the 

 plan, but when very accurate results are desired it will be good practice to make 2 or 3 consecutive measure- 

 ments with the pole arm on one side of the tracer arm and afterward the same number of consecutive read- 

 ings with the pole arm on the other side of tracer arm, and by taking the mean of the averages of readings 

 obtained, very close results will be obtained. 



The Compensation Planimeter is made of German silver and bronzed brass. 

 The tracer arm is adjustable and graduated to the end, pole weight of improved pat- 

 tern. Instrument complete in velvet-lined case, with table of constants for U. S. 

 standard measure, adapting it to any scale. 

 No. 107. Price complete as above . . . . . . . $28.00 



No. 108. " " " " when specially rated . . . 32.00 



