72 Proceedings of the Royal Irish Academy. 



we have had with these countries. It may even be believed that theii- 

 establishment with us does not go farther back than the time of the 

 Crusaders, and that previously we had no knowledge of water-mills, 

 wind-mills, or wells with chains of buckets. 



(p. 94). — The Crusaders, on their return from their foreign 

 expeditions, brought home with them these^and many other'machines, 

 which have been perpetuated and perfected by reason of our require- 

 ments and our learning. It is not the less curious to see from whence 

 they come, how much we owe to the Eastern peoples, and what we 

 have added to theii* inventions. 



I have already given (in the Letters on the Morea, &c., 2nd part, 

 p. 41) a drawing of a well which seemed to me to fulfil cheaply the 

 same object as machines of much more complicated design. I may 

 say the same of two sorts of mills which I had occasion to sketch 

 at Lampsaki : they are of such great simpKcity that the mere in- 

 spection of the drawing should be enough to make the mechanism 

 intelligible. 



This mechanism in the fi.rst mill in question (pi. 5) merely consists 

 of a horizontal wheel divided into rays or spokes, hollowed out so as 

 receive and to oppose the greatest resistance to the water. The iron 

 axis of this wheel passes through the lower millstone, fixes itself 

 by means of a tenant in the form of a H, of which -Yitruvius speaks, to 

 the centre of the upper millstone which it puts in movement. [Note. — 

 This iron, which the Latins called " smSscms," is called " Cothl''^ by 

 the Arabs : they have also given this name to the poles of the world, 

 and they imagine that the sphere of the heavens turns on them and 

 round them as if upon pivots (D'Herbelot, voce " Cothb ").] 



So far there is nothing particularly ingenious in the mechanism, 

 but that which really appears to be so is the care taken, not only to 

 take advantage of the small supply of water, with great skill, but 

 even to double, as it were, its action. If water had been abundant in 

 supply and at all periods, its fall alone would have been sufficient to 

 furnish the movement to a vertical wheel, such as that of our mills ; 

 but it was requisite to meet the difficulty of its insufficiency at certain 

 times, and also to get rid of its excess at other periods. For this 

 purpose the canal is so built as to contain or carry the quantity of 

 water strictly necessary. The excess overflows, before reaching the 

 end of the canal by means of a sluice-gate indicated in the drawing. 



To this end of the canal has been adapted a long box, having the 

 form of a reversed pyramid ; made of planks sufficiently thick, ad- 

 justed and held together by means of strong ties. The joints are 



