He carefully opened the trap door, looked around the roof, and then slowly climbed the remaining steps.  Luna heard some startlingly loud, deep-throated caws protesting the invasion.  After a few moments, he gave the signal for her to follow, and she climbed after him as quietly as possible.  A low wall surrounded her, made of the same dark stone as the rest of The Roost.  Regularly-spaced along the wall were large, square sections rising upward that looked like the teeth carved into a jack-o’-lantern.  Luna knew these were merlons.  They provided cover to defenders of the tower when they were shooting arrows through the gaps (known as crenels) between.  The wall at the crenels was about chest high, while the merlons reached above her head.  Next to the wall was a telescope mounted atop its base.  A well-weathered stool stood beside it.  A short distance away, Luna spied an old, rickety broom closet.  Her father kept two old but working brooms here in case of emergency, and that was why he had taught her the basics of broom flight.  Continuing around the wall, a weather vane sprouted from atop a crenel.  Below that was a simple weather station, with a thermometer, barometer and rain gauge.  Next was some optical contraption.  Several lenses and mirrors were mounted on a complex structure of adjustable metal arms and clamps.  This allowed the lenses and mirrors to be set at different positions and angles.  Last was a tall, magical sundial, as near to the trapdoor and the center of the roof as possible.  It was made of dark, polished granite, well worn by the rain, and may have been an original part of The Roost.  The style⁵ cast a shadow on the face of the dial.  Around the edge of the dial were engraved characters.  They displayed the date, the hour, the minute and the second in Roman numerals.  The engraved numerals changed with each second’s passing.