Like a wheel within a wheel.
A piece of pipe with a mark at each end is set rotating and spinning at the same time. Amidst the blur of the moving cylinder, one of the marks appears three times, forming a stationary triangle.
About 2 feet [...]
How Water is Supplied to Dry Areas
Portions of the country, which were unfit for agriculture because of too little rainfall, have been changed into good farming regions by irrigation; water from the mountains being collected in large reservoirs and carried by flumes, pipes, or cemented ditches, for great distances, to where the water is [...]
