1856.] Prof. Tyndall on Cleavage oj Crystals, 295 



VVeale, John, Esq. (the Publisher) — Rudimentary Treatises : — 

 Recent and Fossil Shells; Part 3. 12mo. 1856. 

 Use of Field Artillery ; by Taubert. 12mo. 1856. 

 Key to the Elements of Algebra. 12mo. 1856. 

 Ships' Anchors. 12mo. 1856. 



WEEKLY EVENING MEETING, 



Friday, June 6. 



SiK Roderick I. Murchison, G.C.S. F.R.S. Vice-President, 

 in the Chair. 



John Tyndall, Esq. F.R.S. 



PaCWESSOE OP NATURAL PHILOSOPHY IN THE BOYAL INSTITUTION. 



Comparative View of the Cleavage of Crystals and Slate Hocks. 



When the student of physical science has to investigate the 

 character of any natural force, his first care must be to purify it 

 from the mixture of other forces, and thus study its simple action. 

 If, for example, he wishes to know how a mass of water would 

 shape itself, supposing it to be at liberty to follow the bent of its 

 own molecular forces, he must see that these forces have free and 

 undisturbed exercise. We might perhaps refer him to the dew- 

 drop for a solution of the question ; but here we have to do, not 

 only with the action of the molecules of the liquid upon each other, 

 but also with the action of gravity upon the mass, which pulls the 

 drop downwards and elongates it. If he would examine the 

 problem in its purity, he must do as Plateau has done, withdraw 

 ^the liquid mass from the action of gravity, and he would then find 

 the shape of the mass to be perfectly spherical. Natural processes 

 come to us in a mixed manner, and to the uninstructed mind are a 

 mass of unintelligible confusion. Suppose half-a-dozen of the best 

 musical performers to be placed in the same room, each playing his 

 own instrument to perfection : though each individual instrument 

 migh be a wellspring of melody, still the mixture of all would 

 produce mere noise. Thus it is with the processes of nature. In 

 nature mechanical and molecular laws mingle and create apparent 

 confusion. Their mixture constitutes what may be called the 

 noise of natural laws ; and it is the vocation of the man of science to 

 resolve this noise into its components, and thus to detect the 

 " music " in which the foundations of nature are laid. 



The necessity of this detachment of one force from all other 



