Generally if S denotes any closed surface, fixed in the fluid, M the mass of the fluid inside it at any time t, and 0 the angle which the outward-drawn normal makes with the velocity q at that point, **dM**/dt = rate of increase of fluid inside the surface, (I) =flux across the surface into the interior _ - f f pq cos OdS, the integral equation of continuity.

Equation (5) becomes, by a rearrangement, dK **dmdm** **dm** din dx dt +u dx + dy +Zee dz + dx (dt +u dx +v dy +w d) = o,.

**Dm** **dm** Dl (8), dx - dx dt + dx dt = °' ...'

**Dm** **dm** Dl (8), dx - dx dt + dx dt = °' ...'

Denoting the cross-section a of a filament by dS and its mass by **dm**, the quantity wdS/**dm** is called the vorticity; this is the same at all points of a filament, and it does not change during the motion; and the vorticity is given by w cos edS/**dm**, if dS is the oblique section of which the normal makes an angle e with the filament, while the aggregate vorticity of a mass M inside a surface S is M - l fw cos edS.

Putting dJ /**dm** =o at constant volume, we obtain as the condition of equilibrium of the two states J' + p'v' = J" -}- p "v".

The function G is represented by the negative area D"**DM** under the isothermal, bounded by the isopiestic **DM** and the axis of pressure.

But since M is constant, **dM** = Sda+adS =o.

As the three molars and (almost invariably) the first premolar of the permanent series have no predecessors, the typical milk-dentition would be expressed as follows: di, dc i, **dm** 3 =28.

It was with them that the Moslem theology - the science of the word (Ka/**dm**) - first came into existence.