Surveying Instrument Collection
Maker 
Brunsviga, Grimme Natalis & Co. 
Model 
Twin 18R 
Serial Number 
232519 
Dimensions 
Length 300mm, Width 210mm, Height 165mm 
Image 

Description 
This Calculating Machine is an early mechanical calculating machine manufactured around the early 1930's. It is a machine specially developed for survey calculations and consists of two single machines mounted together, so that both can be turned by the single crank handle. One machine always rotates in the same direction as the handle, but, by means of a control lever, the other can be controlled so that it rotates in the same direction, the opposite direction or remain stationary. It is a mechanical design where a number on the key is added into an accumulated total by pulling a lever. It has provision for sliding the accumulator section so that a number can be added or subtracted at any position within 10 figures. It will perform the four fundamental arithmetic operations  addition, substraction, multiplication and division. The obvious application of twin machines is to cases where two numbers are multiplied by a common multiplier, as when the sine and cosine of an angle are multiplied by a length, which occurs when resolving bearing and distance into rectangular coordinates. 
History & comments 
The Brunsviga calculating machine has been, in the past, the most widely applied arithmetic instrument. Brunsviga was also the first company to introduce the concept of mounting together two single calculating machines to produce the Twin Brunsviga series. 
Conservation 
In a container 
Condition 
Good 
Remarks 

Dates 
Manufactured in 1933 (approx.). Catalogued in 1997 