184 AN EMPIRICAL STUDY OF GYRATING BODIES. 

 THE "GYROSTATIC BALANCE." 



At the meeting of the British Association at Montreal, 

 Sir William Thomson, in a paper entitled, "Steps To- 

 ward a Kinetic Theory of Matter," read a description of 

 a new instrument which he called a gyrostatic balance. 

 His paper, together with a wood cut representing the in- 

 strument, has been widely published in scientific jour- 

 nals. That in Nature, for Aug. 1884, page 419, is now 

 before me. 



The balance consists of four "gyrostats," 1 connected 

 by joints, which allow no lateral motion. "It might 

 have been constructed of two members, but four are 

 shown in the diagram for symmetry." Together they 

 form a kind of square enclosed in a spherical shell — the 

 latter being "of no use except to prevent the interior 

 being seen." At the uprjer corner of the square is a 

 hook by which to suspend it, and at the lower, another 

 hook to which a weight may be attached. 



The four " gyrostats " are wound up all in one direc- 

 tion, and then set going at once. Of course they all re- 

 volve in one direction,!, e., if their axes were in a line all 

 the wheels would be rotating in the same sense. This 

 Sir William indicates very plainly by his directional el- 

 lipses. 



Now hang them up by the upper hook, and attach a 

 moderate weight to the lower hook. 



Sir William affirms the following four propositions, al- 

 though not in the same order : 



1. There will be no rotation about the vertical axis — 

 and of course no horizontal rotation. 



2. A weight attached to the lower hook will vibrate 

 up and down, as if attached to the hook of a spring bal- 

 ance. 



1 Gyrostats only in name and form. In reality they are gyroscopes, since they are sup- 

 ported at one end of the axis, while in the gyrostat the point of support is in the plane of 

 the wheel. 



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