Dry Ice Slide Rule
The temperature here is -9°F and still dropping, so I thought it might be an appropriate time to post a picture of this odd little circular slide rule.
This slide rule belonged to my grandfather, who was a meat inspector for the US Department of Agriculture. The slide rule was used to calculate how much dry ice was needed to fill a railroad car to keep a load of beef frozen until it reached its destination. The back side bears the date 1954.
This slide rule belonged to my grandfather, who was a meat inspector for the US Department of Agriculture. The slide rule was used to calculate how much dry ice was needed to fill a railroad car to keep a load of beef frozen until it reached its destination. The back side bears the date 1954.