C. GENERAL PHYSICS. 135 



C. GENERAL PHYSICS. 



THE RELATION BETWEEN GRAVITATION AND ENERGY. 



In a paper on the relation of the law of gravitation to the 

 principle of the conservation of energy, Rev. George P. 

 Young, of Toronto, proposes to show that if this principle be 

 accepted, it must follow that the force of gravitation, which, 

 at ordinary sensible distances, is one of attraction, must at 

 a certain limit necessarily undergo a transformation into a 

 force of repulsion. He concludes, moreover, that there is a 

 higher law than that of conservation of energy, which law is 

 expressed by him in certain mathematical formula?, from 

 which he deduces both the law of gravitation at ordinary 

 limits, and the law of repulsion within certain limits. Ccma- 

 dian Journal of Science^ XIV., 589. 



Thomson's dead -beat arrangement for chemical 



balances. 



In ejivins: an account of Sir William Thomson's arrange- 

 ment for lessenino; the vibrations of delicate chemical bal- 

 ances, Professor Tait states that this method consists in 

 suspending from the beam two very light closed cylinders, 

 which fit closely, but without touching, into two fixed cylin- 

 ders open at the top. This apparatus, when applied to a 

 long and massive beam which ordinarily vibrated for some 

 minutes when disturbed, brought it to rest in three half vi- 

 brations. There is therefore practically no limit to the 

 length and consequently to the sensibility that may be given 

 to the balance beam. 



An instructive aero-dynamical phenomenon is noted by 

 him in this connection, viz., the closed cylinder, when exactly 

 balanced inside of the open cylinder, can be made to ascend 

 briskly by a current of air, even when the latter blows verti- 

 cally downward upon the centre of the upper end of the 

 cylinder. Proceed, of the Roy. Soc. of Edinburgh, VIII., 491. 



SIMPLE DYNAMOMETER. 



Dr. Hamilton, of the Long Island College Hospital, mentions 

 that, having a necessity for a dynamometer for therapeutical 



