 The fourth stage involved <unk> the problem of communicating between the two towers during the time of Pope Pius X. His plans were to make the Gregorian Tower into a historical tower and to record and carry out observations at the second tower by linking the two towers along the fortified wall with a 83 metres ( 272 ft ) iron bridge spanning the gap . At the west end of this bridge , a four @-@ inch equatorial was installed on semicircular <unk> . The east end of the bridge , above the barracks of the gendarmes , had a <unk> , with a camera attached , used to photograph the Sun ( <unk> ) . A new 16 @-@ inch visual telescope , called Torre <unk> X , was erected in the second tower . As a result of these modifications , the original library was moved to the <unk> Academy <unk> , and the old meteorological and seismic instruments were shifted to the <unk> di <unk> observatory . The new Astronomical Library was housed in two rooms of the building . The two new <unk> machines were used for recording on the <unk> plates . The recorded observations were published along with <unk> notes together with the last two series of the <unk> of stars . Charts were printed on silver bromide paper . 
