Ten shafts lined with slabs of tufa which were there found may have been the approaches to tombs or may have served as wells.
It is noticed that labourers employed in deep mines worked by shafts suffer less from fever than do those who are engaged in stripping the alluvial deposits.
In cases where the direction of the air motion is always the same, as in the ventilating shafts of mines and buildings for instance, these anemometers, known, however, as air meters, are employed, and give most satisfactory results.
Each coil is attached to a shaft by a bell crank arrangement, and to these shafts there is secured a system of levers similar to that at the transmitter carrying the receiving pencil at the junction.
The shafts are turned by the pull of the magnet upon the coils, and the motions of the transmitting pencil are thus reproduced.