474 Prof. Osborne Reynolds on the Dilatancy of Media 



So long as the arrangement of the shot is such that 'there is 

 enough water to fill the interstices the shot are free, but any 

 arrangement which requires more room is absolutely prevented 

 by the pressure of the atmosphere. 



* If there is an excess of water in the bag when the shot are 

 in their maximum density, the bag will change its shape quite 

 freely for a limited extent, but then becomes instantly rigid, 

 supporting 56 lb. without further change. By connecting 

 the bag with a graduated vessel of water so that the quantity 

 which flows in and out can be measured, the bag again becomes 

 susceptible of any amount of distortion. 



Getting the bag into a spherical form and its contents at 

 maximum density, and then squeezing it between two planes, 

 the moment the squeezing begins the water begins to flow in, 

 and flows in at a diminishing rate until it ceases to draw more 

 water. 



The material in the bag is in a condition of minimum den- 

 sity under the circumstances. This does not mean that all 

 the parts are in a condition of minimum density because the 

 distortion is not the same in all the parts ; but some parts 

 have passed through the condition of maximum while others 

 have not reached it, so that on further distortion the dilations 

 of the latter balance the contractions of the former. If we 

 continue to squeeze, water begins to flow out until about half as 

 much has run out as came in ; then again it begins to flow in. 

 We cannot by squeezing get it back into a condition of uni- 

 form maximum density, because the strain is not homogeneous. 

 This is just what would occur if the shot were frictionless ; so 

 that it is not surprising to find that, using oil instead of water, 

 or, better (on account of the india-rubber), a strong solution 

 of soap and water, which greatly diminishes the friction, the 

 results are not altered. 



On measuring the quantities of water, we find that the 

 greatest quantity drawn in is about 10 per cent, of the volume 

 of the bag ; this is about one third of the difference between 

 the volumes of the shot at minimum and maximum density. 



—/- : 1, or 30 per cent, of the latter. 



On easing the bag it might be supposed that the shot would 

 return to their initial condition. But that does not follow : 

 the elasticity of form of the bag is so slight compared with 

 its elasticity of volume, that restitution will only take place as 

 long as it is accompanied with contraction of volume. 



So long as the point of maximum volume has not been 



