Not only was he the first discoverer of the rotifers, but he showed "how wonderfully nature has provided for the preservation of their species," by their tolerance of the drying-up of the water they inhabit, and the resistance afforded to the evaporation of the fluids of their bodies by the impermeability of the casing in which they then become enclosed.
In Cheshire the surface-water trickling through the overlying strata dissolves the salt, which is subsequently pumped as brine, but at Middlesbrough the great depth and impermeability of the strata precludes this, so another method has been resorted to.
But the crust of the earth varies from almost complete impermeability to almost complete permeability.
Thus despite the impermeability of its mass large springs are occasionally found to issue from the Lower Chalk.
By these means practical impermeability was obtained.