1. Find a large, flat space in your garden on which the sun can shine directly with no shadows of trees, buildings &c. interfering.
2. Mark out your hour lines with "room enough for the guns."
3. Place one cannon without ball but with powder on one o' clock, two cannons on two o' clock, and so on and so forth.
4. Place twelve burning glasses around gnomon so that when the sun shines directly on the glasses they alight.
5. Create a gunpowder trail along each hour line that leads from the burning glass to cannon(s).
All together, Mr Franklin explains, there will be 78 guns. Won't the neighbors be pleased to know it is 8am when they hear the eight cannon shots go off? Mr Franklin goes on to explain that the chief expense will be in the powder since with proper upkeep the cannon will be good for at least 100 years. He also notes how cloudy days will also curtail costs.
But let me give Mr Franklin the last word, for this is his creation:
"Kind Reader, Methinks I hear thee say, 'That it is indeed a good Thing to know how Time passes, but this Kind of Dial, notwithstanding the mentioned Savings, would be very expensive; and the Cost greater than the Advantage.' Thou art wise, my Friend, to be so considerate beforehand; some Fools would not have found out so much, till they have made the Dial and tried it. Let all such learn that many a private and many a publick Project, are like this Striking Dial, great Cost for little Profit."