154 



WIND-MILL, (on mechanics.) 



the indigo will be separated as a blue or 

 green powder, which will yield a ):)urple 

 smoke when placed on a hot iron. It 

 may also be dissolved in sulphuric acid, 

 which, with indigo, forms a permanent 

 blue solution. 



If the indigo is mixed with green fe- 

 cula, as in woad, the plant must be ex- 

 hausted by water, and then treated with 

 boiling alcohol. The first solutions con- 

 tain much of the fecula, but the succeed- 

 ing ones, which are bluish, contain more 

 of the indigo. If these solutions are eva- 

 porated almost to dryness, and alcohol 

 again added, it will take up the fecula, 

 and leave the indigo. 



Indigo ought to be looked for in Ga- 

 lega officinalis, (goal's rue,) from whence 

 Linnaeus says, a fine blue color is ex- 

 tracted; and in Scabiosasiiccisa,{<\ew'iVs 

 bit,) from whence the Swedes prepare a 

 blue fecula, by treating it in the manner 

 of woad. The plants which yield per- 

 manent green colors, probably contain, 

 besides indigo, a yellow coloring matter. 



The above process is also considered 

 free from the unwholesome effluvia pro- 

 duced by the old method. 



Jinn, cle Chini. 



WIND MILL (on mechanics.) 

 (Continued from page 16.) 



That the wind may act with the 

 greatest efficiency upon the^ sjtils, the 

 wind shaft must have the same direction 

 as the wind. But as this direction is 

 perpetually changing, some apparatus is 

 necessary for bringing the wind shaft and 

 sails into their proper position; this is 

 done by turning the axis and sails round 

 in a horizontal direction. There are two 

 methods of effecting this. In the old 

 mills the whole of the mill or building 

 which contains the machinery is sustained 

 upon a vertical post, firmly fixed as a 

 stand or foot, upon which the whole 

 machine can be turned by a lever, to 

 present the sails to any quarter of the 

 horizon from whence the wind blows; 

 and hence these are called post wind 

 mills; and are necessarily made of wood. 

 The other kind is called a smock mill, in 

 which only the dome cap or head which 

 contains the axis of the sails and covers 

 the great cog wheel, turns round horizon- 



tally; the other parts of the machinery 

 being contained in a fixed building which 

 rises up in a form of a conical tower of 

 masonry, and is surmounted by the mov- 

 able cap or dome, which is supported on 

 rollers, so as to turn round easily. 



As both the common methods of ad- 

 justing the wind shaft require human 

 assistance, it would be very desirable 

 that the same effect should be produced 

 solely by the wind. This may be done 

 by fixing a large wooden vane or weather 

 cock at the extremity of a long horizontal 

 arm which lies in the same vertical plane 

 with the wind shaft. 



By these means when the surface of 

 the vane and its distance from the centre 

 of motion is sufficiently great, a very 

 gentle breeze will exert a sufficient force 

 upon the vane to turn the machinery, and 

 will always bring the sails and wind shaft 

 to their proper position. This weather 

 cock, it is evident, may be applied either 

 to machines which have a movable roof, 

 or to those which revolve upon a vertical 

 arbor. 



This method is practised in small 

 machines; but a vane of sufficient power 

 to turn a large mill about would be un- 

 wieldy. A much better method is there- 

 fore practised in the best mills. 



The head is contrived to turn itself 

 about whenever the wind changes, in the 

 following manner: — A small pair of sails, 

 or fans are fixed up in a fr^me projecting 

 from the back part of the head, it has a 

 pinion of 10 leaves upon its axis, engag- 

 ing in a wheel of 60 teeth upon an in- 

 clined axis ; and this has a pinion of 12 

 leaves at the other end of it, turning a 

 bevilled wheel of 72 teeth upon a vertical 

 iron axis, at the lower end of which is a 

 pinion of 11 teeth; this works in a circle 

 of 120 cogs, fixed round on the out side 

 of the fixed kirb. By these means, when- 

 ever the fan is turned, it moves the head 

 of the mill slowly round, and in propor- 

 tionate power. The axis turns in the 

 circle which contains 120 cogs. 



Note. It is supposed that the axis of 

 the fan wheel shall be at right angles to 

 the other so that when either turns, the 

 other will be at rest. Sails may be ad- 

 justed to any force of wind in the follow- 

 ing manner. Suppose a wind wheel to 



