Kircher noted that once objects had been magnetised, they continued to have a relationship with each other even when they were at a distance. He therefore proposed a “machina cryptologica”; this consisted of a number of bottles at some distance from each other, with the letters of the alphabet inscribed around the middle of each bottle. Each also had a lubricated and magnetised stopper bearing a pointer. When the stopper on one bottle is rotated so that the pointer indicates a particular letter of the alphabet, the stopper on the other bottles rotates in the same way. Thus by turning the stopper in one place, someone could send a message to a person observing the bottle at the other end of the machine.