WINDPIPE WINDOW. 



Smeaton on this subject (Philosophical Transac- 

 tions, 1759), it appears that the following positions 

 are the best. Suppose the radius to be divided 

 into six equal parts, and call the first part, begin- 

 ning from the centre, one, the second two, and so 

 on, 'the extreme part being six : 



.V jl 



56 



the Axil. 



TV- 



71 



78 



74 



77* 

 83 



Aigte with the 



r.t,.- ... v , 01 



An*i< ef WMUer. 



18 

 19 

 18 

 16 



As it is necessary that a windmill should face the 

 wind from whatever point it blows, the whole ma- 

 chine, or a part of it, must be capable of turning 

 horizontally. Sometimes the whole mill is made 

 to turn upon a strong vertical post, and is therefore 

 culled a post mill ; but, more commonly, the roof or 

 head only revolves, carrying with it the windwheel 

 and its shaft, the weight being supported on fric- 

 tion rollers. In order that the wind itself may re- 

 gulate the position of the mill, a large vane, or 

 weathercock, is placed on the side which is oppo- 

 site the sails, thus turning them always to the 

 wind. But in large mills the motion is regulated 

 by a small supplementary windwheel, or pair of 

 sails, occupying the place of the vane, and situated 

 at right, angles with the principal windwheel. 

 When the windmill is in its proper position, with 

 its shaft parallel to the wind, the supplementary 

 sails do not turn. But when the wind changes, 

 they are immediately brought into action, and, by 

 turning a series of wheelwork, they gradually bring 

 round the head to its proper position. 



Adjustment of Sails. On account of the incon- 

 stant nature of the motion of the wind, it is neces- 

 sary to have some provision for accommodating the 

 resistance of the sails to the degree of violence 

 with which the wind blows. This is commonly 

 done by clothing and unclothing the sails ; that is, 

 by covering, with canvass or thin boards, a greater 

 or smaller portion of the frame of the sails, accord- 

 ing to the force of the wind at different times. A 

 method has been devised for producing the same 

 effect, by altering the obliquity of the sails ; and 

 windmills have been so made as to regulate their 

 own adjustment by the force of the wind. If we 

 suppose a windmill, or windwheel, to consist of 

 four arms, and that the sails were connected to 

 these arms at one edge by means of springs, the 

 yielding of these springs would allow the sails to 

 turn back when the wind should blow with violence ; 

 and their elasticity would bring them up to the wind 

 whenever its force abated. This effect has been 

 produced by a weight acting on the sails through a 

 series of levers. A loose iron rod, passing through 

 the centre of the axle of the windwheel, receives 

 the action of the weight at one end, and communi- 

 cates it to the sails at the other. 



WINDPIPE (trachea); a cartilaginous and mem- 

 branous canal, through which the air passes into the 

 lungs. Its upper part, called the larynx, is com- 

 posed of five cartilages, the uppermost of which, 

 called the epiglottis, closes the passage to the lungs, 

 when a person is in the act of swallowing. The 

 two front cartilages of the larynx, the thyroides, or 

 Adam's apple, and the annular, which resembles a 

 ring, may be felt directly under the skin. The 

 various cartilages of the larynx are united to each 

 other by elastic fibres, and are enabled, by their 



several muscles, to dilate or contract the passage, 

 and perform those numerous motions which render 

 the larynx so important as an organ of the voice ; 

 for, when the air passes directly into the trachea 

 through a wound, it produces little or no sound. 

 (See Voice.') From the larynx the cunal takes the 

 name of trachea, and, after extending as far down 

 as the fourth or fifth vertebra, it divides into two 

 branches, running to the two lobes of the lungs, to 

 which they are distributed by an infinite number of 

 branches. The trachea is furnished with muscular 

 fibres, by the contraction or relaxation of which it 

 is enabled to shorten or lengthen itself, and also to 

 dilate or contract the diameter of its bore. The 

 cartilages of the trachea, by keeping it constantly 

 open, afford a free passage to the air, which we are 

 obliged to be incessantly respiring ; and its mem- 

 branous part, being capable of contraction or dilata- 

 tion, enables us to receive and expel the air fli ;t 

 greater or less quantity, and with more or 

 velocity, as may be required in singing and decla- 

 mation. (See Respiration. For the structure of 

 the windpipe in birds, see Ornithology.') This 

 membranous structure of the trachea posteriorly, 

 seems likewise to assist in the descent of the food 

 by preventing that impediment to its passage down 

 the oesophagus, which might be expected if the 

 cartilages were complete rings. 



WIND SAILS, in a ship, are made of the com- 

 mon sail-cloth, and are usually between twenty- 

 five and thirty feet long, according to the size of 

 the ship, and are of the form of a cone ending ob- 

 tusely. When they are made use of, they are 

 hoisted by ropes to about two thirds or more of 

 their height, with their bases distended circularly, 

 and their apex hanging downwards in the hatch- 

 ways of the ship. Above each of these, one of the 

 common sails is so disposed that the greatest part 

 of the air, rushing against it, is directed into the 

 wind sail, and conveyed into the body of the ship, 

 to promote ventilation, &c. 



WINDERMERE; a celebrated lake in the 

 county of Westmoreland, the most extensive sheet 

 of water in England. It is situated at the foot of 

 the Furness fells, and is distinguished by the variety 

 of beautiful prospects which it exhibits. It is 

 about fifteen miles in length from north to south, 

 and about one broad on an average, though in many 

 places much less. 



WINDHAM, SIR WILLIAM. See Wyndham. 



WINDHAM, WILLIAM. See Supplement. 



WINDOW. In the most ancient eras, the win- 

 dows of habitations were very small and narrow 5 

 and the same remark is true of the castles and 

 other edifices which were constructed during the 

 middle ages. In the painting on the Greek vase 

 which represents Jupiter about to scale the window 

 of Alcmena, the opening is exceedingly small. Ac- 

 cording to Seneca, those of the baths of Scipio 

 were so small that they merited not the name, 

 and might rather be denominated crevices. As the 

 Romans improved, however, in the elegant arts, 

 this particular was not overlooked ; and both their 

 town and country houses were decorated with 

 numerous and ample windows. It was not custo- 

 mary to have them overlooking the street; and 

 they were, in the majority of instances, confined to 

 the interior court of the house. The ancient tem- 

 ples had not, generally, windows : some exceptions, 

 however, exist to this observation. Before the use 

 of glass became common, which was not till to- 

 wards the end of the twelfth century, the window? 



