ON THE MANUFACTURE OF SALT IN CHESHIRE. 9 



the velocity at which Stokes's solution would fail is in- 

 versely as the radius of the sphere, if failure can take place 

 through want of cohesion *. 



It becomes necessary now to consider the result of such 

 a failure. In a perfect fluid, the consequence must be dis- 

 continuity, since we cannot admit any minimum value of 

 <j), and therefore of ir, within the fluid. In a real fluid, on 

 the other hand, the possibility of the fluid under the tension 

 failing to exert pressure equally in all directions would 

 have to be considered as intermediate between the usual 

 problem and that of disruption. In either case vortex 

 motion would ensue behind the solid. 



IV. On the Manufacture of Salt in Cheshire. 

 By Thomas Ward, Esq. 



Eead November ist, 1881. 



The manufacture of salt has been carried on in Cheshire 

 from the times of the Romans; and as the brine-springs in 

 several places rose to the surface or nearly so in early times, 

 it is quite possible that the Britons may have utilized them. 

 We have no record of salt-making during the early Saxon 

 times, though doubtless it existed; for in Domesday Book 



* Or, otherwise, consider the sphere to be brought to rest; the whole 

 motion of the fluid will then cease. But in order to produce rest an impul- 

 sive tension of the magnitude named must be sustained at the surface of the 

 sphere. 



