98 AN EMPIRICAL STUDY OF GYRATING BODIES. 



is to be classed with the Bohnenbergher ; and precession 

 and nutation are problems in the mechanics of that 

 machine. 



The top has been known from time immemorial. The 

 gyroscope came into prominent notice some thirty years 

 ago. It is perhaps an outgrowth of the Bohnenbergher, 

 as that is considerably the older. The gyrostat is a 

 modification of the gyroscope, first made by Sir William 

 Thomson. The gyrocycle is another modification of the 

 same instrument, invented and named by the writer of 

 this paper. 



The literature of these bodies is meagre. Scattered 

 through the proceedings of various learned societies are 

 quite a number of papers relating to the gyroscope, but 

 scarcely any relating to the others. 1 On examination it 

 will be found that these papers are, for the most part, 

 merely descriptive. The explanations offered are scant 

 and unsatisfactory. Going outside of "proceedings," 

 we find a somewhat extensive discussion of the Bohnen- 

 bergher, and the gyroscope, in a lecture on " Planetary 

 Disturbance," by Prof. Snell, read before the Smith- 

 sonian Institution, 1855. There is quite an article in 

 the Ency. Brit., 9th ed. The explanation there given 

 and the mode of treatment are substantially identical 

 with that of General Barnard, published in the Amer. 

 Journ. Ed., vols. 3, 4, and 5, and afterwards republished 

 in the Amer. Journ. Science for 1857. A similar ex- 

 planation appears in Johnson? s Cyclopedia. The last 

 of General Barnard's papers includes a brief discussion 

 of the top. There is a somewhat extensive article upon 

 the gyroscope and gyrostat in Thomson & TaW s Nat. 

 Phil. There is also one in the English Cyclopedia. 



Frisfs celebrated law was formulated with special 

 reference to precession, and will be treated of when we 

 come to that subject. 



1 An incomplete list of such papers is given in Ency. Brit., 9th ed., article "Gyroscope." 



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