On 26th October 1935 I obtained specimens of the glacial clays exposed in the section described by Bisat1 at the top of the chalk pit at Hesslewood, near Hessle. They were put into new stout paper bags and have been kept in a dry cupboard ever since. On recently taking out the bags I was astonished to find that one of them felt damp; it contained a sample of the chalky boulder clay near the bottom of the section. This and all the other clays mentioned in the paper were examined in the following way: about two and a half ounces (say 70 grammes) of the clay were put in a beaker, covered with distilled water, stirred at intervals until the clay had all disintegrated, and then allowed to settle, the supernatant liquid being then filtered off and evaporated to small bulk; when cold, a small quantity was tested with silver nitrate and the remainder was allowed to evaporate spontaneously. The concentrate from the Chalky Boulder Clay and the Lower and Upper Hessle Clays of the Hesslewood section all yielded crystals of sodium chloride large enough to be visible under a pocket lens and even to the naked eye. The Chalky Clay and the Lower Hessle Clay contained much about the same amount, the Upper Hessle containing slightly less. Gypsum also crystallised out. On the same day in 1935 specimens were also taken of the clays in the section described by Stather2 at Redcliff, North Ferriby. The lower boulder clay ...