436 Scientific Intelligence. 
cies are found in every latitude and in every country. For example, 
such common forms as Achnanthidium lanceolatum, Achnanthes evilis, 
Gomphonema tenellum, G. constrictum, G. capitatum, Cocconeis Placen- 
tula, C. Pediculus, Cocconema lanceolatum, C. cymbiforme, Synedra 
radians, Navicula elliptica, N. rhomboides, Pinnularia viridis, P. 
major, P. oblonga, P. borealis, Surirella biseriata, S. ovata, Meridion 
circulare, M. constrictum, Cymbella maculata, C. scotica, C. cuspidata, 
Epithemia turgida, Ep. Argus, Himantidium Arcus, H. gracile, H. 
majus, Odontidium mesodon, Diatoma tenue, D. vulgare, Nitzschia 
linearis, N. amphioxys, Melosira varians, and many others actually 
occur in every part of the world from whence these soils have come ; 
and there is absolutely no difference between the exotic and the British 
orms. 
Ehrenberg specifies tw6 species, namely, Pinnularia borealis (P. 
latistriata, W. G.) and Eunotia amphioxys (INitzschia amphioxys, W. 
Sm.), as having been found by him in almost every instance. My re- 
sults confirm this. In no case have both of these been absent, and in 
at least nine-tenths of these soils both are present. They are often 
the predominant forms, and in a few cases almost the only forms pres- 
ent. Gomphonema tenellum and Achnanthidium lanceolatum are foun 
in a large majority of these soils. 
am disposed to agree in opinion with Ehrenberg, that the miero- 
scopic organisms found in soils contribute materially to the increase of 
the soil. is is true both of the siliceous and caleareous forms. The 
Diatomacee live in moist earth. They obtain silica from the water, 
and at their death their shells are added to the soil. Where many are 
present, this process of transference of silica from the rock to the soil 
goes on very rapidly. We have so far evidence that they live in these 
soils, that we find them there very often in the state of self-division, 
which is not observed in old accumulations of the dead shells. 
The peculiar capacity of the Diatomacee for resisting climatic 
changes, whereby the same species can live and thrive as well in 
Arctic circle as under the line, corresponds well with the results of the 
study of the same organisms in the fossil state. In Ehrenberg’s ‘Mi- 
krogeologie’ will be found very fine figures of the Diatoms occurring 1n 
the different forms of Bergmehl, Tripoli or polishing slate, Kieselguhr, 
pumice, and other volcanic rocks, mountain limestone, amber, Wc., 
and it will be seen that by far the greater number of the species are 
quite identical with recent ones. Microscopic organisms have been 
found so low down as the green sand of the Silurian system ; but they 
rather belong to the Polythalamia. The earliest Diatoms, geologically 
speaking, as figured by Ehrenberg, agree in every point, as far as the 
great majority of the species is concerned, with those now living !n our 
waters, and forming deposits which will become rock at some futu 
me, 
It was supposed that most of the species in the much more recent 
Bergmehl were no longer to be found living; but most of them have 
been since found. I myself have lately found two species of the Lap- 
land Bergmehl to be still in existence, namely, Eunotia octodon and 
Synedra hemicyclus ; and Eunotia incisa, which occurs both in the 
Lapland and the Mull earths, has been found recent by me in a dozen 
wy 
