294 HOW WE FOUND THE MICROZOA. 



Tlius, a flood of light was tlirown on a subject which had puzzled 

 even the late Professor Edward Forbes, who suggested the " ploughing 

 up action of ice-bergs, and the sweeping action of great waves coming 

 from the north." But the mud of the boulder clays requhed a stUl sea 

 for its deposition ; and its depth in Lancashire and Cheshire may be 

 judged fi'om the fact that the upper boulder clay of Macclesfield is 

 700 feet, and of Amfield, Cheshire, upwards of 600 feet above the sea 

 level ; yet the broken and fragmentary shells of the Mollusca occur 

 throughout at all levels, and are all littoral orsub-httoral in their habits — 

 some Uving on rocks, others on sand, others on sea-weeds, yet found in a 

 common matrix of red clay — none of the bivalves with valves united, and 

 all more or less broken. 



The presence of the glaciated erratics and arctic Mollusca tells us 

 the climate was severe enough for the formation of ice in the winters 

 along the then shores, when the north of England was sunk, perhaps, a 

 thousand feet or more beneath the glacial sea; when glaciers ground 

 their way down the valleys of Wales and the Lake district, sending forth 

 their turbid streams of mud into the sea to form the boulder clays. 

 Along these shores lived the Mollusca ; from these shores the ice-rafts 

 distributed them over the sea-bed, together with the glaciated stones 

 with which they lie entombed, which bed, since upraised, has become the 

 plains of Lancashire, Cheshhe, and, pei'haps, the MidJSind Coimties. 

 The gi-anite boulders in the boulder clays of Lancashire and Cheshire 

 have been traced to their soi;rces in.Eskdale, Cumberland, and Criffel, 

 Scotland ; and their distribution extends far beyond the limits of these 

 counties, in a southerly direction. There is, therefore, a fair field of 

 research open to the Midland Geologist in the boulder clays of those 

 districts. The boulder clays of the north-west of England were once 

 thought to be azoic, yet they have jaelded to research a large fauna. 

 In the upper boulder clay of Newton-by-Chester, I have found 148 

 species of Mollusca, Ostracoda, Foraminifera, &c., where no one thought 

 of looking for a shell before 1873. 



A word or two in conclusion may be spared for the middle sands and 

 gravels, which occupy considerable areas in Lancashire and Cheshire. 

 Professor Hull, M.A., F.E.S., wasthe first to obsei-ve that the di-ift clays and 

 sands and gravels could be separated into three divisions — 1st, in descend- 

 ing order — an upper boulder clay ; then, 2nd, tliis was succeeded by 

 (middle) sands and gi-avels ; and, 3rd, a lower boulder clay. The 

 physical featm-es and the fauna of the upper and lower boulder clays are 

 very similar, except that the lower boulder clay bears evidence of more 

 glacial conditions than the upper. All the phenomena I have described 

 are applicable to both clays. The middle sands and gravels differ from 

 the boulder clays — first from the total absence in them (except near the 

 mountains) of glaciated stones. The shells, too, of the Gastropoda are 7iot 

 filled vdth Mici-ozoa, like those of the clays, but with the coarse sand or 

 fine gravel, in which they aie generally found embedded. The rolled 

 character of the broken shells of the MoUussa also jjoiuts to a difi'oreut 

 mode oi distribution to those of the boulder clays. 



