DR. J. MOllISOX — ICE AND ITS "WORK. 155 



cliiilk wliirli it contains. "We Hud in it ice-scratched flints, tlint- 

 pebbles, boulders of chalk, some large unworn Hints, quartzites, 

 sandstones, and grits, and various derived Jurassic fossils. A 

 mammoth's tooth was found here some years ago, and other mam- 

 malian remains have been discovered. A mass of boulder-clay 

 occurs to the east of St. Albans between Beaumont's Farm and 

 London Colney. From a well which was lately sunk near Tyttcn- 

 hanger in tliis area through the clay, I obtained lum})s of chalk 

 with glacial striae and also derived Jurassic fossils. Mr. Arthur 

 Smith, of Hill End Farm, Smallford, has obtained from this bed 

 various Jurassic fossils and also a vertebra of a fish. Eoulder- 

 clay in Hertfordshire is made up of chalk to a great extent, con- 

 taining lumps of chalk and chalk- flmts as well as fragments of 

 Jurassic rocks and Jurassic fossils. We also find in smaller 

 quantity portions of Carboniferous rocks, slates, and fragments 

 of (|uartz, quartzite, and granite. 



Besides the Boulder- clay we have another glacial deposit in 

 various parts of the country known as Drift. This consists mainly 

 of gravel and sand mixed up together in varying proportions, but it 

 may contain seams of clay or brick-earth, as is well seen in the 

 pits in Miskin's brickyard near St. Albans. The drift may be 

 well studied in this neighbourhood in almost any gravel-pit. Drift 

 gravel is made up of pebbles, rolled or sub -angular, the majority 

 of them derived from local rocks, but containing a considerable 

 number composed of rocks foreign to the neighbourhood. In 

 Hertfordshire it consists mostly of flint-pebbles, but also contains 

 sub-angular and unworn flints, sometimes of considerable size. It 

 also contains large masses of conglomerate, the well-known Hert- 

 fordshire pudding-stone, which are often finely polished, especially 

 on their fractured surfaces. Fragments of chalk are also to be 

 found in it. The stones which it contains derived from rocks foreign 

 to the locality are mostly quartz, quartzite, sandstone, and igneous 

 rocks. Boulders of quartzite and sandstone of considerable size 

 sometimes occur in it. In some localities, as in the gravel-pit 

 near Welwyn Station, we find rolled Jurassic fossils — Gryplma 

 and Belemnites. Fragments of Arctic shells are also found in this 

 pit. In the neighbourhood of St. Albans, and also in other parts 

 of the county, fossils derived from the Chalk are not uncommon. 

 In Bricket Wood and in other parts of Hertfordshire the drift may be 

 traced underneath the boulder-clay, showing that in this case it is 

 of earlier age. I may mention, however, that there are other 

 boulder-clays not represented in this county which are lower 

 than the MidcUe Glacial Drift, as the drift which occurs in this 

 neighbourhood has been called. 



The boulder-clay was probably the moraine prnfonde of an 

 enormous ice-cap which covered the greater part of our country 

 and was pushed out into the shallow seas, where Arctic shells 

 were mixed with it, so we may suppose that the localities 

 where the clay contains those shells were under water at the 

 time when it was deposited. When the drift on the other hand 



