 Galileo made a number of contributions to what is now known as engineering , as distinct from pure physics . Between 1595 and 1598 , Galileo devised and improved a Geometric and Military Compass suitable for use by gunners and surveyors . This expanded on earlier instruments designed by Niccolò Tartaglia and <unk> del Monte . For gunners , it offered , in addition to a new and safer way of elevating cannons accurately , a way of quickly computing the charge of gunpowder for cannonballs of different sizes and materials . As a geometric instrument , it enabled the construction of any regular polygon , computation of the area of any polygon or circular sector , and a variety of other calculations . Under Galileo 's direction , instrument maker Marc 'Antonio Mazzoleni produced more than 100 of these compasses , which Galileo sold ( along with an instruction manual he wrote ) for 50 lire and offered a course of instruction in the use of the compasses for 120 lire . 
