Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
What Are Little Boys Made Of? Iona and Peter Opie, this first appears in a manuscript by the English poet Robert Southey (1774–1843), who added the stanzas other than the two below. Though it is not mentioned elsewhere in his works or papers, it is generally agreed to be by him. The relevant section in the version attributed to Southey was: <poem> What are little boys made of What are little boys made of Snips & snails & puppy dogs tails And such are little boys made of. What are little girls made of Sugar & spice & all things nice</poem> Extracts from the nursery rhyme