76 Henry Riddel/ on 



sketch-book is still preserved at Paris. He says : " Many a time 

 have skilled workmen tried to contrive a wheel which will move 

 of itself ; here is one way, and is by an uneven number of mallets 

 or with quicksilver." I have not been able to obtain a copy of 

 his drawing, but it is evidently similar in principle to many which 

 follow it. The great engineer and architect, Leonardo di Vinci, 

 also believed himself to have solved the problem, but of his inven- 

 tion also I have failed to obtain a copy, though it seems to have 

 been of the w-eighted wheel type. Innumerable machines have 

 been designed and constructed on these principles, their authors 

 being confident of their complete success, but somehow they 

 failed in the performance. Such inventions were specially 

 numerous between the time of di Vinci and that of the Marquis 

 of Worcester, but almost without variety. Wilkin carefully 

 examines the idea, and by means of a method of moments con- 

 vinces himself that the device cannot succeed. He tells us that 

 he used the science of Trochilics, or wheeled constructions, and 

 with Aristotle as his authority upon the balance, he is convinced 

 that such wheels are always in equilibrium. 



There are, however, two records in this class of invention so 

 historically interesting that a short notice is necessary, that in- 

 vented by the Marquis of Worcester, and that constructed about 

 fifty years later by Orphyreus. 



The famous Edward Somerset, Marquis of Worcester, who 

 died in 1667, describes this wheel in the " Century of Inventions ^^' 

 which seems to have been written between 1645 and 1655. The 

 date is not quite certain, indeed one authority states that it was 

 first published in 1648, while it is often said that it was first 

 printed in 1663, four years before the death of the author, while 

 the book itself seems to be dated 1659. The text runs; — "To 

 provide and make that all the weights of the descending side of a 

 wheel shall be perpetually further and further from the centre than 

 those upon the mounting side, yet equal in number and heft the 

 one side to the other ; a most incredible thing if not seen, but 

 tryed before the late King of happy and glorious memorye in the 

 Tower by my directions, two extraordinary ambassadors accom- 



