The behaviour suggested by the title of this talk is rather different from that of our daily experience. Indeed many materials, such as blood, emulsion paints, modern lubricating oils, new alloys, plastics of all kinds and so on, have properties which are different from those of ordinary liquids and solids.

The response to stress of some of these materials can be spectacularly diferent from that of viscous liquids or elastic solids; they exhibit behaviour which cannot be adequately explained by the simple mathematical laws of the classical theories.

The unusual behaviour of some of these materials will be discussed and a brief review will be made of some fairly recent developments in the formulation of mathematical equations which can explain such behaviour.

The meeting will be held at 6 p.m. on Tuesday 2nd May, in the Engineering Lecture Theatre of the University of Malta (entrance through car park 2). Entrance is free for members, and a token donation of 25c to cover expenses (and coffee!) is requested from non-members.

The Malta Mathematical Society may be contacted c/o Department of Mathematics, University of Malta, Msida; tel. no. 3290-2380; Web Page: http://www.maths.um.edu.mt/MathSoc/ ; Email: mathsoc@maths.um.edu.mt