WIND-MILL. 



loaded to a maximum, afe confiderably quicker than the 

 velocity of the wind. 



Rules for modelling the Sails of Wind-Mills. — Fig. 4. 

 Flatell. Wind-Mill, is a front view of one of the four fails of 

 a wind-mill. The letters of reference will ferve to explain 

 the terms made ufe of in the following defcription. 



1. The length of the arm or whip A A, reckoned from 

 the centre of the great fhaft B, to the outermoft bar 19, 

 governs all the reft. 



2. The breadth of the face of the whip A, next the 

 centre, is one-thirtieth of the length of the whip ; its thick- 

 nefs at the fame end is three-fourths of the breadth ; and 

 the back-fide is made parallel to the face for half the length 

 of the whip, or to the tenth bar ; the fmall end of the whip 

 is fquare, and as its end is one-fixtieth of the length of the 

 whip, or half the breadth at the great end. 



3. From the centre of the {haft B, to the neareft bar i 

 of the lattice, is pne-feventh of the whip ; the remaining 

 fpace of fix-fevenths of the whip is equally divided into 

 nineteen fpaces, fo as to make nineteen bars ; one-ninth of 

 one of thefe fpaces is equal to the mortifes for the bars, the 

 tenons of which are made fquare where they enter and go 

 through the whip, and confequently the mortifes mull be 

 fquare alfo. 



4. To prepare the whip for mortifing, itrike a gage- 

 fcore at about three-fourths of an inch from the face on each 

 fide, and the gage-fcore, on the leading fide 4, 5, will give 

 the face of all the bars on that fide ; but on the other fide, 

 the faces of all the bars will fall deeper than the gage-fcore, 

 according to a certain rule. To find the fpace to be fet off 

 for this purpofe fpr each bar, conftruft a fcale in the fol- 

 lowing manner. 



5. Extend the compaffes to any diftance at pleafure, fo 

 that fix times that extent may be greater than the breadth 

 of the whip at the feventh bar ; fet thofe fix Ipaces oft upon 

 a ftraight line for a bafe, at the end of which raife a per- 

 pendicular ; fet off three fpaces upon the perpendicular, and 

 divide the two fpaces that are fartheft from the bafe line 

 into fix equal parts each, fo that this quantity of two fpaces 

 may be equally divided into twelve fpaces marked out by 

 thirteen points ; from each of thefe points draw a fine to 

 the oppofite end of the bafe, as fo many rays to a centre, 

 and the fcale is finiflied. 



6. To apply this fcale to any given cafe, fet off the 

 breadth of the whip at the lad bar, ( that is, the bar at the 

 extremity of the fail,) from the centre of the fcale along 

 the bafe towards the perpendicular ; and at this point raife 

 a perpendicular to cut the ray neareft to the bafe ; alfo fet off 

 the breadth of the whip at the feventh bar in the fame man- 

 ner, and at this point ereft another perpendicular to cut the 

 thirteenth radius. From the interfeftion of the perpendicular 

 (drawn upon the breadth of the laft bar) with the firft of 

 the thirteen radii, to the interfeftion of the other perpendic ular 

 with the thirteenth radius, draw an oblique line cutting all 

 the reft, and the diftances of each of thefe laft-mentioned 

 points of interfedlion from the bafe line is the fpace which 

 the face of each bar is diftant from the gage-line on the 

 driving fide. 



7. Thefe diftances give a different fet-off" for each bar 

 till the feventh, which fame muft be fet off for all the reft 

 to the firft. 



8. The mortifes muft be fquare to the leading fide of the 

 whip. 



9. When the mortifes are cut, let the face of the whip 

 be floped off fo as to agree with the face of the bars in 

 every part. 



10. Two-fifths of the whip are the length of the laft or 

 longeft bar. 



11. Five-eighths of the longeft bar muft be on the dri»- 

 ing fide of the whip, and three-eighths on the leading fide, 

 each being reckoned from the middle of the whip. 



12. The proportion of the mortifes already given deter- 

 mines the fize of the bars at the mortifes, but their thick- 

 nefs muft be diminiftied each way, fo as to be only one -half 

 at the ends ; but the face muft be kept of equal breadth all 

 the way. 



13. The leading fide goes no farther than the fourth bar, 

 and there only projefts one-third of the proieftion of the 

 laft bar. 



14. All the bars on the driving fide are made hollowing 

 in the arch of a circle, which begins to fpring one-third of 

 the length of the bars on the driving fide from the whip ; 

 and the fweep is fuch, that if a ftraight line is applied to 

 the face of the bar from the whip to the end, the face of 

 the bar fhould leave the ftraight fine about the breadth of 

 the bar. 



15. There ought to be three uplongs, as 3, 2, la. Jig. 4, 

 to the driving, and two to the leading fide, as at 5, 4, to 

 ftrengthen the lattice. 



Self-regulaling wind-mills are thofe which adapt theni- 

 felves to the irregularities of the wind, by diminiftiing or in- 

 creafing the furface on which the wind can aft to turn them 

 round. If the wind increafes in force, the furface expofed 

 to its aftion is diminiftied ; on the contrary, if it decreafes 

 in force, the furface will be ihcreafed in the fame pro- 

 portion, fo as in fome meafure to render their motion 

 uniform. 



The following felf-regulating wind-mill is ftated as the 

 invention of Mr. Andrew Mickle in 1772, the inventor of the 

 threftiing-machine. The length of the fail was divided into 

 eleven compartments, by the bars forming a number of oblong 

 openings, which were each filled up by a fquare frame of 

 wood covered with canvas, and mounted on pivots at their 

 ends ; one pivot turning in a hole in the whip, and the other 

 in the bar which lies parallel to it, in the manner of a Venetian 

 blind : the pivots were not placed in the middle of the breadth 

 of the frames, but at one-third from that edge, towards the 

 ftiaft or axis of the fails. On the end of each pivot which 

 enters the whip a fmall roller is fixed, round which a chain 

 paffes, and its end is attached to a fteel fpring, placed at 

 right angles to the whip, and in the direftion of the length 

 of the canvaffed frames. Now, if the wind blows too hard, 

 it afts to turn the frames edgeways, in which cafe the wind 

 pafles through the fails, and exerts lefs force to turn them 

 round ; but as foon as the wind becomes moderate, the fteel 

 fpring brings up the frames into a plane, prefenting their 

 whole furface to its aftion. A rod of iron extends the 

 whole length of the whip, and is connefted with the feveral 

 fprings, to afford the means of ftrengthening or diminiftiing 

 their aftion, according to the feafon of the year. This rod 

 was formed into a fcrew at its outer extremity, and a nut 

 put on to enable the miller to adjuft the ftrength of the 

 fprings conveniently, from the circular gallery furrounding 

 the outfide of the mill. 



Mr. Wilham Cubit of North Walfham, in the county of 

 Norfolk, took out a patent, in 1807, for a method of 

 equalizing the motion of wind-mill fails. It is fimilar to 

 Mr. Mickle's, in the fails being made like a Venetian 

 bhnd ; but inftead of the fprings, he applied racks and 

 pinions on the ends of the bhnd pivots, and a Aiding rod, 

 which paffed in a fmall hole made through the length of the 

 axis of the fails ; the end of this rod within the mill was 

 3 R 2 made 



