130 Mr. E. Hunt on certain I'lwiomena connected with 



On certain Phenomena connected with Rotatory Motion, the Gyroscope, 

 Precession of the Equinoxes, and Saturn's Bings. By Edmund Hunt, 

 Secretary to the Institution of Engineers in Scotland {with a Plate). 



The subject of Rotatory Motions is one of the most interesting to be 

 found in mechanics, and very much has already been written about it. 



In 185-i, Mr. EUiot, then of Edinburgh, received a prize niedail, value 

 .£10, from the Royal Scottish Society of Arts, for a paper bearing on 

 this subject ; and the same paper was, I understand, afterwards read 

 before yourselves. From The Transactions oftlie Royal Scottish Society 

 of AHs, I find that the subject has been brought before them several 

 times since, by Mr. Elliot, Professor Sang, and Professor Smyth. In 

 1854, Professor Baden Powell read a paper on the subject at the Royal 

 Institution of Great Britain, London ; and more recently a very elaborate 

 paper on the subject has been written by Major J. Gr. Barnard, A.M., 

 Corps of Engineers, U.S.A., and is given in Sillimans Journal for July, 

 1857. Mr. Elliot's explanation is peculiar to himself; Major Barnard 

 follows the French mathematician, Poisson, who wrote on the subject 

 in 1818 or thereabouts ; and in the Report of Professor Powell's paper 

 a detailed explanation is not given, but allusion is made to a variety of 

 earlier authorities, in such a way as to convey the impression that they 

 are all unanimous, whereas to me they seem otherwise. The number 

 of Silliman's Journal for November, 1857, contains a short paper on 

 the gyroscope, by Professor Newton ; and a lecture on the subject hag 

 very recently been delivered before the Liverpool Literary and Philoso- 

 phical Society, by Professor Hamilton. I have here briefly alluded to 

 the most modern writers on the subject, but it has been touched upon 

 to a greater or less extent by almost all the most celebrated mathe- 

 maticians and astronomers since Newton's time. 



In the present paper I do not propose to deduce results by means of 

 profound analytical investigations, but shall attempt to follow and 

 explain the actions under consideration in a simple and popular manner, 

 and, in doing so, I shall pass over much old ground, so as to make per- 

 fectly intelligible anything new I may have to say. 



A true explanation of the phenomena of the gyroscope is founded on 

 what is known as the principle of the composition of Rotatory Motion. 

 Professor Powell says this principle was originally discovered and 

 demonstrated by Frisius in 1750; I find, however, that it was clearly 

 stated, though not demonstrated, nearly a century earher, by Newton, 

 in one of the Corollaries to the remarkable 66th Prop, of the 1st book 

 of the Princiina. Playfair states the theorem in his Outlines of Natural 

 Pldlosophy, and refers to Frisius' demonstration. He says : " When 

 a body revolves on an axis, and a force is impressed, tending to make it 



