sentences:  At the beginning of the 20th century, complex rules governed the composition and number of candles to be used at Mass.Lighted candles of the correct composition (beeswax, with no more than a minimal admixture of other material, and usually bleached) were considered so essential that, if before the consecration they happened to go out (quenched, for instance, by a gust of wind) and could not be relit within fifteen minutes, the celebration of Mass had to be abandoned, and some writers maintained that even if the candles could be relit within that time, Mass should in any case be begun again from the start.Some of these rules were formulated only in the second half of the nineteenth and the beginning of the 20th century.