THE jacket for Stephen Friar's Companion to Cathedrals and Abbeys states, rightly, that even in this secular age, Britain's cathedrals remain potent symbols of religious continuity. Cathedrals are majestic yet humbling places. Even the most strident atheist will whisper almost reverentially in the presence of centuries old Gothic arches or knight-draped tombs. Yet the details of so much of what constitutes a cathedral is, pardon the pun, a closed book to so many of us — this guide, with more than 1,450 A to Z listed entries, widens our knowledge of the architecture of these great buildings and the rituals connected with them. Exeter Cathedral features frequently, not least for the use of Dorset's Portland stone in its construction in 1303 and the tierceron (ribs which extend from the upward splay of a vault to its apex) vaulting of its nave, described in the book as probably the finest in Europe. And above that nave is the mysterious carved stone Minstrels' Gallery in which angels are depicted playing musical instruments. Wells Cathedral in Somerset is famed for its 14th century clock-jack in which the bells that mark the hours and quarter-hours are struck by carved and painted figures. Perhaps a little less well known is the 'scissor arches' at Wells, created to halt the cracking and leaning of the tower. This is not a pocket-sized reference book to plot your way around the architectural features of Britain's cathedrals, but it is a fascinating guide to religious practices and architectural features. Oh, and the questions posed in the heading? A Galilee is a somewhat controversial term used to describe a vestibule reserved as a chapel for penitents at the western end of a nave. A Loculus is a recess in an altar in which relics were kept, and a Walking Place in churches of the mendicant orders was a passage formed by crosswalls between the nave and the choir. l The Sutton Companion to Cathedrals and Abbeys by Stephen Friar is published by Sutton Publishing, price £25.