A barcode is a series of alternating dark and light stripes that are read by an optical scanner. The organization and width of the lines is determined by the bar code protocol selected. There are many different protocols, such as the prevalent Code 39. Sometimes the digits represented by the dark and light bars are also printed to allow people to read the number without an optical reader.
When searching for a memory card, it's important to consider more than just capacity. It's nice to have a big warehouse to store data, but speed, data protection, and durability are just as important for high performance in demanding conditions. Speed refers to the rate at which data can be stored. The faster your card, the more images you'll be able to shoot in a single burst, and the less lag and fewer interruptions you will experience.
In 1958, the English-born Spiritualist C. Dorreen Phillips wrote of her experiences with a medium at Camp Chesterfield, Indiana: "In Rev. James Laughton's séances there are many Indians. They are very noisy and appear to have great power. [...] The little guides, or doorkeepers, are usually Indian boys and girls [who act] as messengers who help to locate the spirit friends who wish to speak with you."
Many 19th century mediums were discovered to be engaged in fraud. While advocates of mediumship claim that their experiences are genuine, the Encyclopædia Britannica article on spiritualism notes in reference to a case in the 19th century that "...one by one, the Spiritualist mediums were discovered to be engaged in fraud, sometimes employing the techniques of stage magicians in their attempts to convince people of their clairvoyant powers." The article also notes that "the exposure of widespread fraud within the spiritualist movement severely damaged its reputation and pushed it to the fringes of society in the United States."