part 3] L02SS, etc. of the uvini am coast. 177 



A sample of the grains of the residue of more or less uniform 

 size which remained on a 240-mesh sieve, but passed a 200-mesh 

 sieve, was examined under a microscope. 



The Durham samples showed angular quartz-grains of all shapes 

 and sizes, the angles scarcely if at all rounded. Mica-flakes were 

 very plentiful, and on the washed surface of some of the concretions 

 they were seen to be arranged in all directions indiscriminately. 

 A residue of another sample showed flakes of light and dark mica 

 and little masses of calcreted loess, together with the angular sharp 

 quartz-fragments already mentioned. The residues of the Bonn 

 loess showed angular quartz-grains, with the edges and corners 

 slightly rounded off. Mica -flakes were not very plentiful, but 

 fragments of land shells, tubular calcareous structures, and bits of 

 vegetable matter were present. These, however, do not occur in 

 the Durham loess. 



Except for the presence of terrestrial shells in the former, the 

 Bonn hess and the Durham lcess are very similar in colour and 

 porosity, and the appended series of analyses show that the Bonn 

 material closely resembles in chemical composition some portions of 

 the loess of the Durham coast. 



1 analysed three samples of the Durham lcess, taken from the 

 lower undisturbed portions in the cliff-section containing the con- 

 cretions, within a few yards of one another, and made an analysis 

 of the inner portion of one of the hard calcareous concretions. 

 For comparison, I also made an analysis of the above-mentioned 

 loess from Kreuzberg, near Bonn. 



Loess from 

 Lfcssfrom Durham Coast. Bonn. 



r 



Loess L. Loess LL. Loess LIL. Loess Concretion. Lcess. 



Per cent. Per cent. Per cent. Per cent. Per cent. 



SiO- 64*87 65-42 6633 4145 63'65 



A1 2 3 2-57 921 9-86 257 5*16 



Fe. 2 3 515 6-45 533 411 537 



OaC0 3 17-66 1P98 904 4425 1828 



MgC0 3 3-76 602 5"40 7*00 4*48 



j£ o q o-rq not esti- not esti- not esti- ,.qo 



""-'" mated mated mated 



Na 2 1-65 „ „ „ 1-45 



Water T06 0'29 093 055 Trace 



Totals ... 99-21 98-37 96'89 99'93 100'32 



In all the samples of the loess the silica is high, and seems to 

 vary but slightly in amount, except in the concretions, where of 

 course its percentage is reduced. The alumina varies to some 

 extent: in some places it is low, and in others rather high, reaching 

 nearly 10 per cent. 



The iron, which is completely oxidized, is comparatively high 

 in all samples, and seems constant in quantity. The lime appeal's 

 to be present as very finely-divided calcite, is variable in amount, 



