overall: 10 1/2 in x 5 in x 4 1/2 in; 26.67 cm x 12.7 cm x 11.43 cm
overall: 10 1/4 in x 4 1/2 in x 3 13/16 in; 26.035 cm x 11.43 cm x 9.68375 cm
Object Name:
double mill
Description:
A double mill apparatus demonstrated the relation between the angle of a wing and the effect of air resistance. The form was known in the eighteenth century. Joseph Henry, the physicist who served as the founding Secretary of the Smithsonian, probably acquired this example for the Institution.
Ref: Jean Antoine Nollet, Lectures in Experimental Philosophy (London, [1748]), pp. 166-167.
James Ferguson, Lectures on Select Subjects in Mechanics, Hydrostatics, Pneumatics, and Optics (London, [1764]), pp. 112-113.
