In laying by line of metal he was confronted by the dispart, ie the difference between the diameters of base ring and muzzle, for it can easily be seen that if he laid the gun with the line of metal horizontal the axis of the bore would be slightly elevated. So he had to measure the dispart by poking a vent pricker down the vent and so measure the distance from the bottom of the bore to the base ring, then measure from the bottom of the bore to the top of the muzzle, and calculate the difference. He could then either make an allowance for the dispart when laying or construct a makeshift foresight and tie it to the muzzle. By the 19^th century guns were being made with a dispart patch to make the height of the muzzle from the bottom of the bore the same as the height of the base ring. As a further step he could fabricate graduated rods for various ranges.

But better things were on the way; around 1545 Tartaglia invented the gunners quadrant. With this instrument plus intensive training in the judging of distance a Number One was able to relate range achieved to elevation on the gun, and thus able to compile a range table of sorts.

The quadrant was normally used only on the heavier guns for more deliberate shooting, eg during sieges. In field artillery where ranges were comparatively short the No 1 deduced the required elevation from experience. The quadrant remained in use for some three hundred years after its invention. During the latter half of the 18^th century some were modified by substituting a spirit level for the plumb line and bob.

Another means of applying elevation to siege or garrison guns before the introduction of the tangent sight was the use of quarter sight scales. These were cut on either side of the base ring and used in conjunction with notches cut on either side of the muzzle. They enabled up to 3° elevation only to be applied, and were so-named because they were graduated in quarters of a degree. Means of applying more elevation would have been superfluous because at 3° the range of the 24-pr firing roundshot was only 1500 yards, by which time its effectiveness, even against wooden ships, would have been minimal.

The tangent sight made the layer's job much easier because he could lay for both line and elevation simultaneously, but it was some time before it was generally accepted. Although invented c1779 few guns were fitted with it before 1800 owing to traditional opposition to new-fangled ideas. When offered the new sight, Nelson said he 'would not look at it' but felt the Royal Navy did not need sights because they always closed to within point blank range before opening fire. Before the appearance of the tangent sight attempts were made to modify the level and/or the perpendicular to apply elevation by placing it fore and aft upon the centre line at the breech (after the line had been found) and after making any adjustment for taper in the barrel. Laying in this manner wasn't very satisfactory but no doubt was more convenient than using the Gunners Quadrant at the muzzle. A rigid plummet instead of plumb line and bob was sometimes used. Spirit levels instead of plumb line etc were tried late in the 17^th century but owing to their cost were not generally adopted until much later.