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"A" Mill Explosion

Title: Diagram of a Dust Collector
Type: Diagram
Date: 1876
Source: Minnesota Historical Society

Description: The dust collector in this diagram was designed and patented to prevent the dangerous build-up of flour dust two years before the Washburn "A" Mill explosion. These collectors gained wider use in the United States after the explosion in Minneapolis.

Diagram of a Dust Collector


  1. This machine was used for milling grain into flour. The grain would be put in the hopper at the top of the machine and ground between the two stones in the center of the drawing. Why would a machine that grinds grain need a dust collector?

  2. The patent on this machine was given in 1876 and the Washburn A Mill exploded in 1878. What could that tell you about whether this machine was used at the time it was patented?

  3. An engineer who came to the Falls after the explosion had actually talked to the inventor of this machine in 1876. The inventor had been unable to convince people to believe his machine was needed at that time. Why might he not have been able to convince them? Why might that have changed after the mill explosion?

  4. How can a drawing like this help you as a researcher understand a machine or a process better than a written description of the same machine or process?