MECHANICAL AIDS IN STEM ANALYSIS 685 



Calculating-machines and most adding-machines have similar key- 

 boards and are of the first type. The calculating-machine simply re- 

 quires the depression of keys to operate. They may be operated by the 

 touch system if only the lower half of the keyboard is used. They are 

 very rapid in multiplication and are fairly rapid in division. The chief 

 objection to their use is that no record of the work is preserved. The 

 Burroughs or Wales machines furnish a printed slip, but when used 

 for listing two columns at the same time zeros are printed as well as the 

 desired figures. It is difficult to use them for multiplication and divis- 

 ion and to operate them by the touch system. 



The simple ten-key Dalton machine commends itself to the forester, 

 in that the touch system is readily learned and that the split-key device 

 enables the listing and adding of the two columns separately. The 

 repeat key and the key make multiplication very easy and rapid. 

 Sufficient accuracy is obtained in division by using a table of recip- 

 rocals. (Multiply the dividend by the reciprocal of the divisor.) 



To sum up, the slide-rule takes care of fairly small numbers in 

 multiplication and division and is very rapid. An adding-machine will 

 list and add two columns at the same time, and whole pages of tables 

 may be printed and totaled by shifting the carriage. The field is almost 

 unlimited. 



