Eye chart number). The denominator indicates the distance in feet at which a person with normal vision could stand to correctly identify the same symbols identified by the person tested. For example, a visual acuity of 20/20 is considered normal. Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision. There is often also a need to test a subject's vision at near or occupational tasks (such as reading or computer use). For these situations, a Rosenbaum
About the Mystery of the Letters Father respectively. The final chapters of the treatise engage in speculation about more general topics, including the history of mankind – whose key events are related symbolically to the sequence of vowels and consonants in the alphabet –, a discussion of Christology dealing with issues related to the Council of Chalcedon, and reflections upon the name of "Adam". About the Mystery of the Letters About the Mystery of the Letters (, "Peri tou mystēriou tōn grammatōn") is an anonymous Christian treatise containing a mystical doctrine about the names and forms of the Greek and Hebrew letters. It was probably written