Why are most of the manholes on roads circular in shape?R. Benitha, Salem, Tamil NaduWhy is the nib of a fountain pen split?S. Alagiavanan, Coimbatore, Tamil Nadu* * *Readers can send questions/answers on science and technology for the Question Corner along with their names and address to the following email id: questioncorner@thehindu.co.in or to The Editor, The Hindu (Science and Technology), 859-860, Anna Salai, Chennai 600 002.