Gilson Atlas Binary Calculator

The Gilson Atlas Calculator was designed by George W. Richardson in the second half of the 1910's, with the idea to perform arithmetic operations with a better precision than the achieved with regular 10-12 inches long rules. Despite the fact that only had two logarithmic scales, one of them was a 46 feet long circular spiral (interior) while the other one was 30 inches long (exterior), allowing these lengths perform arithmetic operations with a precision of three to five figures. In 1919 Richardson sold his business and designs to the Gilson Slide Rule Co., a company in those years established in Niles, Michigan, USA. In 1922 Gilson patented an enhanced design of the Atlas Calculator. The models produced in the 1920's had the circular scales printed on a 10 inches square aluminum base, and two transparent celluloid cursors. 

In 1931 the Atlas Calculator (Type II) became a 8.25 in diameter circular dual rule, having on the opposite side the Trigonometric Scales Sines and Tangents of the Midget Circular root copyrighted that same year:  In this new model the scales were shorter, 26 inches the circular exterior, and 39 feet the spiral interior. it was fabricated also on aluminum and coated in white plastic. 

Same as its Binary Circular Slide Rule, not only Gilson marketed the Atlas Calculator., but also other companies like Dietzgen, Post, Lietz, Bruning, and Compass, even though the rule was never branded or labeled by them, only the user manual specifies the company. 

Click on the next links to see professional panoramic pictures of the Atlas Calculators models:

Atlas Calculator Square Base

https://www.sliderulemuseum.com/Circular/Gilson_AtlasSquareCalculator_Type1_RodLovetteCollection.jpg

Atlas Calculator Type II

https://www.sliderulemuseum.com/Circular/Gilson_Atlas_8inchCircularSlideRule.jpg

References:

• Smithsonian. National Museum of American History. Gilson Atlas Calculator Circular Slide Rule.   https://americanhistory.si.edu/collections/search/object/nmah_1215053 

• Calculating.Wordpress: The Atlas 50 foot Slide Rule. October 28, 2012. https://calculating.wordpress.com/2012/10/28/the-50-foot-slide-rule/