the copies of most of the literary manuscripts that still exist. Manuscripts were not common items. They were expensive and hard to make. First, cows or sheep had to be slaughtered and their skins tanned. The leather was then scraped, stretched, and cut into sheets, which were sewn into books. Then inks had to be made from oak galls and other ingredients, and the books had to be hand written by monks using quill pens. Every manuscript is slightly different from another, even if they are copies of each other, because every scribe had different handwriting and made different errors. Individual scribes can sometimes be identified from their handwriting, and different styles of hand were used in specific scriptoria (centres of manuscript production), so the location of the manuscript production can often be identified. There are four great poetic codices of Old English poetry (a codex is a book in modern format, as opposed to a scroll): the Junius Manuscript, the Vercelli Book, the Exeter Book, and the Nowell Codex or Beowulf Manuscript; most of the well-known lyric poems such as The Wanderer, The Seafarer, Deor and The Ruin are found in the Exeter Book, while the Vercelli Book has the Dream of the Rood, some of which is also carved on the Ruthwell Cross. The Franks Casket also has carved riddles, a popular form with the Anglo-Saxons. Old English secular poetry is mostly characterized by a somewhat gloomy and introspective cast of mind, and the grim determination found in The Battle of Maldon, recounting an action against the Vikings in 991. This is from a book that was lost in the Cotton Library fire of 1731, but it had been transcribed previously. Rather than being organized around rhyme, the poetic line in Anglo-Saxon is organised around alliteration, the repetition of stressed sounds; any repeated stressed sound, vowel or consonant, could be used. Anglo-Saxon lines are made up of two half-lines (in old-fashioned scholarship, these are called hemistiches) divided by a breath-pause or caesura. There must be at least one of the alliterating sounds on each side of the caesura. The line above illustrates the principle: note that there is a natural pause after 'hondum' and that the first stressed syllable after that pause begins with the same sound as a stressed line from the first half-line (the first halfline is called the a-verse and the second is the b-verse).