Page:Popular Science Monthly Volume 92.djvu/713

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��An ingenious adding device that can be operated on the same principle as a dial on an automatic telephone. It is adapted to the work of accountants and bookkeepers

��Simple Adding Machine Conve- nient to Handle

WITH no keys to press and no levers to manipulate, the simple adding machine shown in the accompanying illustration is particularly adaptable to the work of accountants and bookkeepers. The device consists of a base with seven notched dials representing cents, dollars, and tens, hundreds, and so on up to $99,999.99.

The device operates on the same princi- ple as the dial on an automatic telephone. For instance, if you wish to add $3.64 and $42.80, you place the pencil-like stylus which comes with the machine, opposite figure 3 in the dollars column and turn the dial to the right as far as it will go. Similar movements are made for the 6 and the 4 in their respective cents columns. In- side each dial is a large notch or win- dow and the figure 3.64 will be found reg- istered in red figures in these notches in the first three dials from the right. If $42.80 is registered in like manner, the total will appear in red fig- ures on the four dials from the right.

For s u b - traction the same princi- ple is used, except that the totals are shown on the white figures. The machine can also mul- tiply.

��TAR KETTLE

��HEATED TAR. OUT

HOT GASES UNDER. TAR KETTLE, AND UP OUT OF STACK

Combination tar and

��gravel heater device in operation. The furnace is fired from the gravel end

��Heating Tar and Gravel Separately But in One Operation

EMULATING the famous hunter of the olden days who killed two birds with one stone, a New Jersey manu- facturer has recently brought out a com- bination tar and gravel heater that heats these two dissimilar materials quite inde- pendently but with one operation. The device, which is shown in the accompany- ing illustration, is particularly fitted for street paving where block pavements with tar joints are laid.

The apparatus consists of two main parts, a rectangular tar kettle and a Y-shaped gravel-bin, with a furnace extending beneath both parts, from one end to the other. The furnace is fired from the gravel end of the device. The smoke and gases escape through an ordinary stove pipe in the kettle end. The inside of the gravel heater is triangular-shaped while the outside is made up in steps consisting of perforated metal plates. The Y- shaped top acts as a reservoir bin and the gravel feeds down the steps and out at the bottom. The perfora- tions in the step plates al- low the moist- ure in the gra-

,,7--.^.^ .» vel to escape PWkTES FOR j-i :+.

STEl^M ESCAPE readily as it is turned into steam by the heat of the fire, thereby making it pos- sible to heat both tar and gravel.

���GRAVEL BIN

��RERFORATED

��FURNACE

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