Other forms. FIG. 4. ***** Fireman's Respirator. Helmholtz on Hay Fever. In my eyes to a very simple barometer--The aneroid barometer--Barometers and weather--The diving-bell--The diving-dress--Air-pumps--Pneumatic tyres--The air-gun--The self-closing door-stop--The action of _trespass quare clausum fregit_, brought by gentle air-currents, established by slight differences of absorptive power.