3 6 \ Of Things relating to Matbematichg,&c. Part IV 
the Rudder, three Feet and feven Inches. The Keel three 
Feet and about five Inches. 
The Beam or breadth of the Ship, fixteen inches, or 
with rcfpcct to the Keel , as two to five. 
The height of the Round-Houfe, or the Room in the place 
of it, three inches and i Of the Great Cabin , three inches. 
Of the Fore-Cajlle , as much. The depth of the Waft an 
inch and i Of the Holds , fix inches and i. Each of them 
four inches broad. The Vacancy between them, eight 
inches over. Their inner fides not belly d, but plain,and per¬ 
pendicular. 
Thefe are the principal Meafures 5 which I thought fit to 
fet down. The great Advantages of this Form, with re- 
fpect either to the Speed, theCourfe, the Safety of the Ship, 
or otherwife, I leave to the Authors own excellent Hand, 
from whom is expected a particular Account hereof 
An INSTRUMENT, contrived by Sir Chriftopher Wren , 
to dcmonltrate, How far againft the Wind a Ship may 
Sail. Shewing , that the Mechanical Power , to which 
Sailing (efpecially againft the Wind) is reducible, is a 
Wedge: And that a Tranfient Force upon an Oblique Rlane 
will caufe the motion of the Plane , againft the firft 
Mover. 
A TERELLA, or an Orbicular Load/lone, about four 
inches and i in Diametre, with the one half immerfed in 
the Centre of a Plane and Horizontal Table 5 fo as to be like 
a Globe with the Poles in the Horizon. Together with 32 
Needles upon the Margin of the Table. By which the dif¬ 
ferent rcfpcct of the Needle to the feveral Points of the 
Loadjlojie 5 the reduction of the Filings of Steel to Helical 
Lines , or near them , by the Magnetick, Effluvia 5 and 
other particulars may be obferv’d. Contriv'd by the fame 
Perfon. 
Two DIPPING-NEEDLES. Defigned for the taking 
of Longitudes. 
A CANOO. Given by Mr. Hocl<?iel. A fort of Boat fo 
called, ufed in Greenland, and fome other places. Figur’d 
almoft like a Weavers Shuttle. The Wooden-Work is 
made up of five flender pieces, running by the length : 
one, which is round at the bottom or in the place of the 
Keel ; and two flat ones in each fide : Made fteady with 
final! 
