32 REPOKT— 187(3. 



bank. The theoretical view which he had then ofl'ered, he now, for the first time, 

 had verified by practical experiment ; and this experiment he showed in the 

 meeting. The chief point of the new view now experimentally proved was that 

 the water in turning: the bend exerts centrifugal force, but that a thin lamina of the 

 water at bottom, or in close proximity to the bed of the river, is retarded by friction 

 with the river-bed, and so exerts less centrifugal force than do like portions of tlie 

 great body of the water flowing over it in less close proximity to the river-bed. 

 (Jousequeutly the bottom layer flows inward obliquely across the channel towards 

 the inner bank, and rises up in its retarded condition between the inner bank and 

 the rapidly flowing water, and protects the inner bank from the scour, and biings 

 with it sand and other detritus from the bottom, which it deposits along the inner 

 bank. The apparatus showed a small river, about 8 inches wide and an inch or two 

 deep, flowing round a bend, and exhibiting very completely the phenomena which 

 had been anticipated. 



On Metric Units of Force, Energy, and Power, larger tlian those on the Centi- 

 metre- Gram-Second System. Bif Jajies Thomson, LL.D., D.Sc, F.R.S.E., 

 Professor of Civil Engineering and Mechanics in the University of Glasgow. 



The author premises that under the excellent method of Gauss for establishing 

 units of force, a unit of force is taken as being the force which, if applied to a unit 

 of mass for a unit of time, v.ill impart to it a unit of ■\elocity. In the system 

 already adoptL'd by the British Association Committee on Dynamical and Electrical 

 Cnits (Erit. Assoc. Eeport, part i. 187.3, page 222), the Centimetre, the Gram *, 

 and the Second were taken as the units of length, of mass, and of time ; and the 

 unit of force thence derived under the method of Gauss was called the Dyne. 



That force is very small, quite too small for convenient use in all ordinarj' 

 mechanical or engineering investigations. It is about equal to the gravity of a 

 milligram mass, and that force is so small that it cannot be felt when applied to 

 the hand. That system, designated as the Centimetre-Gram-Second System, 

 recommended by the Committee of the British Association, and described fidly, 

 with many applications, in a book since published by Dr. Everett, who was 

 Secretarj' to the Committee, is well suited for many dynamical and electrical 

 pm-poses ; and it ought certainly to be maintained for use in all cases in which it 

 is convenient. But tiie object of the present paper is to recommend the emploj-- 

 nient also of two other systems which are in perfect harmony with it, and to 

 propose names for the units of force under these two systems. 



In one of these systems, the Decimetre, the Kilogram, and the Second are the 

 imits adopted for length, mass, and time ; and thus the sj'stem comes to be called 

 the Decimetre-Kilogram-Second System. 



In the other, the Metre, the Tonne t, and the Second are adopted as the units of 

 length, mass, and time; and thus the system comes to be called the Metre-Tonne- 

 Second System. 



It is to be particularly observed that all the three systems here referred to are 

 framed so as to attain the condition, verv- important for convenience, that the 

 unit of mass adopted is the mass of a unit volume of water, and that, therefore, 

 for every substance tlie specific gravity and the density, or mass per unit of volume, 

 are made to be numerically the same. 



In the Decimetre-Kilogram-Second System, the unit of force derived by the 

 method of Gauss is 10,000 Dynes, or is about equal to the gravity of 10 Grams. 

 It is impossible, or almost so, to work practically with any such system without 

 having a name for the unit of force. The unit of force in this system is such that 

 a human hair is well suited for bearing it as a pull, with ample allowance of extra 



* The spelling Gram, instead of Gramme, for the English word is adopted in tlie 

 present paper in accordance with the spelling put forward in the Metric Weights and 

 Measures Act, 1864, wbich legalizes the use of the Metric System in Great Britaiu nnd 

 Ireland. 



t The Tonne is the mass or quantity of matter contained in a cubic nicire of water, ar.d 

 is very nearly the same as the British Ton. 



