Catholic Encyclopedia (1913)/Altar Lanterns
Lanterns are used in churches to protect the altar candles and lamp, if the latter for any reason, such as a draught, cannot be kept lighted. They are of perforated metal-work or set with crystals. They are used also to accompany the Blessed Sacrament when carried from one altar to another in the church, or when It is carried as Viaticum to the sick. In the former case the lanterns are attached to the top of high staves; in the latter, a ring is fastened to the top as in ordinary lanterns, and they are carried in the hand of a cleric or an assistant.