Page:Life of Sir William Petty 1623 – 1687.djvu/149

 River of Thames, between London and Gravesend, and it was wrought with six horses, worth about 8 or 9l a horse.

With this Engine has bin towed 4 of his Majys. new thirdrate ships, built at Blackwall, from that place to Woolwich, without any masts, vizt. the Kent, Essex, Suffolk, and Exeter.

With the same has bin tow'd down the River from Deptford to severall places divers of his Majesty's 5th and 4th rate Frigatts, when the wind obstructed there; having all their masts and Rigging standing and sails furled. Particularly, the St. David, commanded by Sir Richard Munden, quite thro' Gallions reach, against a stiff gale of wind.

The Engine has likewise tow'd merchants ships deep laden drawing 16 foot water, from Blackwall, Gravesend, in one Tyde.

The said third rate ships were of above 1000 Tonn burthen, and each of them were towed in an houre from Blackwall to Woolwich, which is 3 miles, and 2 of them tow'd against the Wind.

All this was perform'd by the strength of 6 horses going round at a capstern in like manner as if it were to heave up an Anchor.

The Demonstration.—Now if wee knew how to place the like Engine within side a ship, and how to apply as much strength to work it as was applyed on board the Tow-boat, then the same strength will give motion to the ship by itself, at least as well as it used to give motion to the Tow boat and the Ship too.

That the Engine may be so placed in a ship is already set forth; and that like force may be applyed to it, is to bee proved.

Twelve men are allow'd to heave as much at a capstern as an able horse can draw at ye same; and say the strength of 72 men are equall to that of 6 horses.

But wee can place 96 men at 2 capsterns, and 32 upon the swiftings, in all 128; which is about $4/5$ more strength then the strength of 6 horses.

And therefore since ye strength of 6 horses, or 72 men, did give good steerage way to the Towboat and the St. David, against a brisk gale of wind; the strength of 128 men, applyed in the same manner may give fresh way to the St. David (or other like ship) at Sea in a Calme.

This I conceive to be Demonstration, but humbly submit to better judgments.

W. P.

Endorsed.—An Attempt to demonstrate how an Engine may be placed in Frigatts to give them way in a calm.

November 7, '85.