SECT. XLVII. How to Weigh Ships sunk, or Ordnance under Water: or to know what empty Cask will carry any sort of Ordnance over a River.

NIcholas Tartaglia hath well collected from the Learned Archimedes, and hath calculated the Proportion of Stone, and other Mettals, what they will weigh in the Water, and in the Air.

All Men know by reason, that whatsoever is heavyer than so much Water, as the body of the Metal thrusteth out of the place, or Vessel, will sink; and being lighter than so much Water, will swim.

Tartaglia saith, that ordinary Free stone weighing 93 l. in the Air, will weigh but in the Water, which is near as 2 is to 1, between the Free-stone, and the Water. And that Marble-stone that weigheth 7 l. in the Air, will weigh but 5 l. in the Water, which is near as 7 to 2, between the Marble and the Water.

And Iron and Tin, that in the Air weigheth 19 l. will weigh 16 l. in the Water; so it is as 19 to 3.

Brass weighing in the Air 65 l. will in the Water weigh 55 l. and so Brass is to Water, as 65 to 10.

And Lead weighing in the Air 30 l. will weigh in the Water but 27 l. so Lead is to Water, as 30 to 3.

And lastly, Gold in the Air being 17 l. in the Water,* it will weigh but 16 l. so Gold is to Water, as 17 to 1. He also layeth down Rules to weigh Ships, or Guns, or any thing else in the Water, that hath not lain too long, and docked it self in Oaze: for if the thing sunk be upon Sands or Rocks, it will weigh the better. He describes Vessels Loadeu to be brought to the place where the thing is sunk, and a Globe of Glass put in a Frame of Wood, and a place in the bottom of the Glass to put his Head into the concave, he may both see and breath, and by a Windless Rope, and weight to sink it, he may first let down the weight, and after have himself down in that Frame, that is in a form of an Hour-Glass, to the bottom of the Sea, and do the work, and sling the •hip, and Guns, and when he will come up to the top again, to un-wind the Rope, and the Frame will be guided upright, and he and it will come to the top of the water very safe, and fasten this Rope brought from the Ships, and un-lead the Vessels, then will they Buoy up the Ship sunk, or any thing from the ground.

Or by a Float-Stage & Windless, Capston, and Trunk of Leather made so thick, that no Water can come in, and with a pair of Glass Eyes fastned, that no Water can go through, fitted to the Case of Leather within, and two Bladders blown at the brim or too of the Water, made fast to the Case of Leather to swim, the Mouth of the Case,* while the Man goes down with Ropes fit to sling it, and makes them fast at liberty; then hale him up after a time fit, and by your Vessels, as before, and Float-Stage, Heave and Buoy up the thing sunk.

Know this, that 5 Tun of Cask will swim a Canon of 8 or 9000 weight, 4 Tun a Demi-Canon, 3 Tun a Culvering, and 2 Tun a Saker, with all things belonging there∣unto, as Planks and Ropes.