Glass plays an important role in measuring time. Hour glasses made of transparent glass indicate the progress of time, depending on the size of the glass and the fineness and amount of sand inside. The hour glass thus defined fixed time units and, when used as “pulpit clock”, it indicated the remaining time of the sermon to the priest and also to the parish. At the same time sand glasses – called “hour glasses” – had a highly symbolic meaning as “memento mori”, as a reminder of the unalterable passage of time and the mortality of man. Measuring air pressure with the barometer would also not have been possible without glass tubes.