188 Col. Beaufoy on the Construction of Sails. [Sept. 



improvement if a machine was contrived to which could be 

 adapted a variety of segments ; and such an object, I conceive, 

 might be obtained by having the oblique sides made of light 

 materials, and united by a hinge, and a brace furnished with a 

 screw and clamp being placed transversely, one end turning on 

 a centre in one leg, and the other extremity sliding in the oppo- 

 site leg. The triangle might be opened or shut the requisite 

 distance, and fastened. 



Stay-sails designed to be carried on a wind ought not to be 

 cut with a square tack, the stay being a fixture on which the 

 sails turn. One with a square tack is quadrilateral ; it is, there- 

 fore, evident, if the materials of which the sail is composed be 

 inflexible, a sail of this figure, when confined in three points, 

 must remain parallel to the vessel's keel, and consequently pro- 

 duce no other effect than that of driving it bodily to leeward ; nor 

 will the custom of carrying the tack to windward render a sail 

 of this form so efficacious in producing a progressive velocity as 

 one of a triangular shape. 



Formerly, it was usual to have a reef in the topsails to let out 

 when running large, and it is reasonable to suppose some good 

 purpose was to be answered in adopting a plan so inconvenient 

 when suddenly obliged to haul on a wind, as the sail must be 

 reefed before hoisted. Two circumstances, in my opinion, 

 contribute to make a swelling sail, when running large, produce 

 a greater effect than a flat one ; first, because the wind is com- 

 pressed in the hollow or concave part ; and secondly, the convex 

 part passes more readily through the stagnant air in front of the 

 sail ; and I am confirmed in this idea from rough experiments 

 made with a concave cylinder, open at one end, and closed at the 

 other. I found that when the open end was exposed to the 

 wind, it was more resisted than when the other end received the 

 shock. The annexed table shows the resistance of air in ounces 

 avoirdupois, of a cylinder 13-541 inches in diameter and altitude, 

 when exposed to the impulse in the direction of its axis, and 

 likewise when placed in a vertical position. 



Consequently, as the resistance of the cylinder sideways is so 

 much less than that it encounters endways, it is evident that the 

 bellying of the sail is advantageous to the sailing of the ship 

 when before the wind. 



In small sails, where strength is not of so much consequence, 

 it would be preferable to have the cloths horizontal instead of 

 vertical, as is plainly shown by ships' ensigns and flags in general; 



