 Complete the following phrase:  It could also be argued that Niccolò Tartaglias invention of the gunners quadrant see clinometer in the 16th century introduced indirect fire guns because it enabled gunlaying by instrument instead of line of sight. This instrument was basically a carpenters set square with a graduated arc and plumb-bob placed in the muzzle to measure an elevation. There are suggestions, based on an account in Livre de Canonerie published in 1561 and reproduced in Revue dArtillerie of March 1908, that indirect fire was used by the Burgundians in the 16th Century. The Russians seem to have used something similar at 