3 6o SECTION MECHANICS. 



The next kind of prime-movers in order of date to be considered are 

 those that are driven by the wind. 



Although, undoubtedly, the propelling of a ship by sails, and even 

 the winnowing of grain, must have long preceded the invention of a 

 prime-mover driven by water, yet the employment of the wind as a 

 source of motive power for driving machinery appears to be but of 

 comparatively recent date. It is said that the knowledge of this kind 

 of prime-mover was communicated to Europe by the Crusaders on their 

 return from the East, but it is difficult to see what foundation there is 

 for this statement. It appears to be certain, however, that wind motors 

 were commonly employed in France, Germany, and Holland in the 

 thirteenth century. 



We can easily understand that in countries where waterfalls and 

 rapid streams are abundant, the windmill would not (owing to its un- 

 certainty) be resorted to ; on the other hand, in arid countries, or even 

 in countries like Holland, where the streams are sluggish and where 

 there is a large amount of land to be drained, the wind, although 

 still uncertain, would nevertheless be a valuable power, and therefore 

 would be utilized. 



Prime-movers to be worked by the wind appear to have been made 

 practically in only two forms viz., the common one wherein a nearly 

 horizontal axle carries four or more twisted radial sails, and that one 

 wherein the axle is vertical and the arms project from it laterally, 

 either as radial fixed arms, as curved fixed arms, or as arms having a 

 feathering motion similar to that of paddle wheels. Where the arms 

 are straight and fixed, some contrivance must be resorted to, to obtain 

 a greater pressure of wind on one side than on the other. 



Bessoni in his work, " The Theatre of Instruments and Machines," 

 published at Lyons in 1582, describes a windmill with vertical spindle 

 and curved horizontal arms placed in a tower with a wind-guard, and 

 by the drawing shows it working a chain pump. Belidor also says, in 

 article 852, that windmills with vertical axles were well known in 

 Portugal and in Poland, and he describes how " that they work within 

 a tower," the upper part of which was fitted with a moveable portion to 

 act as a screen to one side of the mill. 



I will not detain you by an allusion to the ancient sailing chariot 

 mentioned by Uncle Toby in "Tristram Shandy/' nor will I pause 



