<P> The bones or shells were cleaned of meat and then prepared by sawing, scraping, smoothing and even polishing to create convenient, flat surfaces . The predominance of scapulae and later of plastrons is also thought to be related to their convenience as large, flat surfaces needing minimal preparation . There is also speculation that only female tortoise shells were used, as these are significantly less concave . Pits or hollows were then drilled or chiseled partway through the bone or shell in orderly series . At least one such drill has been unearthed at Erligang, exactly matching the pits in size and shape . The shape of these pits evolved over time and is an important indicator for dating the oracle bones within various sub-periods in the Shang dynasty . The shape and depth also helped determine the nature of the crack that would appear . The number of pits per bone or shell varied widely . </P> <P> Divinations were typically carried out for the Shang kings in the presence of a diviner . A very few oracle bones were used in divination by other members of the royal family or nobles close to the king . By the latest periods, the Shang kings took over the role of diviner personally . </P> <P> During a divination session, the shell or bone was anointed with blood, and in an inscription section called the "preface", the date was recorded using the Heavenly Stems and Earthly Branches, and the diviner name was noted . Next, the topic of divination (called the "charge") was posed, such as whether a particular ancestor was causing a king's toothache . The divination charges were often directed at ancestors, whom the ancient Chinese revered and worshiped, as well as natural powers and Dì (帝), the highest god in the Shang society . A wide variety of topics were asked, essentially anything of concern to the royal house of Shang, from illness, birth and death, to weather, warfare, agriculture, tribute and so on . One of the most common topics was whether performing rituals in a certain manner would be satisfactory . </P> <P> An intense heat source was then inserted in a pit until it cracked . Due to the shape of the pit, the front side of the bone cracked in a rough 卜 shape . The character 卜 (pinyin: bǔ or pǔ; Old Chinese: * puk; "to divine") may be a pictogram of such a crack; the reading of the character may also be an onomatopoeia for the cracking . A number of cracks were typically made in one session, sometimes on more than one bone, and these were typically numbered . The diviner in charge of the ceremony read the cracks to learn the answer to the divination . How exactly the cracks were interpreted is not known . The topic of divination was raised multiple times, and often in different ways, such as in the negative, or by changing the date being divined about . One oracle bone might be used for one session or for many, and one session could be recorded on a number of bones . The divined answer was sometimes then marked either "auspicious" or "inauspicious", and the king occasionally added a "prognostication", his reading on the nature of the omen . On very rare occasions, the actual outcome was later added to the bone in what is known as a "verification". A complete record of all the above elements is rare; most bones contain just the date, diviner and topic of divination, and many remained uninscribed after the divination . </P>

Oracle bones were used by the chinese to tell what happened in the past