During this period, a curious blocklong forerunner of the subway was built nine feet beneath Broadway from Warren to Murray Street: a pneumatic tube with giant rotary blowers pushed an upholstered car carrying 22 people.

Historically many designs of blower have been used, from separate pumping cylinders, 'top hat' pistons combining two pistons of different diameter the larger one being used for scavenging, various rotary blowers and centrifugal turbocompressors, including turbochargers.

The graph shows actual measured dampener performance that equates to over 30 dB reduction in pulsation level at the fundamental pulsation frequency and the first harmonic at a flow rate of 29000CFM @ 68°F from a rotary blower.

The rotary blowers and V-plows had banked the weekend's 95 inches into neat white walls 12 feet high (driving was like moving through an endless white tunnel) and the drifts reached as high as the roofs of cabins and the branches of trees.