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? What Are Little Boys Made Of? "What Are Little Boys Made Of?" is a popular nursery rhyme dating from the early 19th century. It has a Roud Folk Song Index number of 821. The author of the rhyme is uncertain, but may be English poet Robert Southey (1774–1843). Here is a representative modern version of the lyrics: <poem> What are little boys made of? What are little boys made of? That's what little boys are made of What are little girls made of? What are little girls made of? That's what little girls are made of</poem> The rhyme appears in