This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
An earthen jar or crock, with a cover, set in a box containing moist sand will keep butter and milk in hot weather better than a refrigerator. The sand must be kept moist at all times. - Edwin J. Bachman, Jr., Fullerton, Pa.