13 
the sea-bottom bears vegetation. If the above-indicated distribution of the organic 
materials did not take place, therefore, the greater part of the bottom of the sea 
would be bare, not only of vegetation but also of the animal life dependent on 
the vegetation. The latter, as will be shown, has in fact its basis in the organic 
matter originating from the Zostera belt. 
In the deposits on the sea-bottom we almost always find therefore larger 
or smaller quantities of organic materials. The distribution, origin and conditions 
of deposition of this organic matter will be more closely discussed in the sequel. 
2. Historical summary. We may first consider the works which have 
dealt with the nature of the sea-bottom, and we must first mention the »Chal- 
lenger« Expedition (Report of the scientific results of the voyage of H. M. S. 
»Challenger« 1873—76). On this Expedition a very large material was collected, 
which has been worked up ånd published by Wyville Thomson and John 
Murray: »Deep-sea deposits«. From this extensive work we cite only a single 
passage, concerning albuminoid and other organic matters in deep-sea deposits: 
»In the Red Clays and the other truly pelagic deposits the organic matter is much 
less« than in close to the shores. Quantitative determinations of the amount of 
organic matter in the bottom samples were not made. 
These were not made either with the bottom samples collected by the 
»Ingolf Expedition« and which were worked up by Bøggild: »Havbundens Af- 
lejringer« (Den danske Ingolfekspedition I, 3). 
On the other hand, we know more about the deposits of organic material 
in freshwater, in Denmark through Wesenberg-Lund's excellent investigations 
in our freshwaters. (Studier over Søkalk, Bønnemalm og Søgytje, Medd. f. D. 
geologisk Forening Nr. 7). According to these investigations a very considerable 
amount of organic material is deposited on the bottom of our deeper lakes, afford- 
ing food for a rich animal life, which exists on the bottom of the lakes. The 
bottom-soil is passed through animals in this way and thus a bottom deposit is 
formed, which in accordance with v. Post is called by the name gytje, by which 
is understood »the bottom deposits formed in pure clean water chiefly by the 
excremental agency of the bottom-fauna«. According to Wesenberg-Lund the 
organic parts of the lake-gytje arise either from the neighbouring land's plant 
and animal world, from the littoral zone of the lake or from plankton. In the 
different lakes these sources are of somewhat different importance. In the case of 
the plankton the results are stated as follows: »In the larger and deeper lakes the 
soft parts are dissolved before the plankton sinks to the bottom, so that it is only 
deposited in the form of skeletal parts. In shallow lakes on the other hand the 
soft parts of the plankton also enter into the composition of the gytje. 
3. Methods for the study of the sea-bottom. To obtain samples of the 
sea-bottom two apparatus have been used, the 0,, m? bottom-sampler constructed 
by C. G. Joh. Petersen to be described later (see Chap. VI). I need only remark 
here, that with the help of this apparatus we obtain a piece of the bottom "/,, th 
of a m? in its natural position, without the separate layers being mixed. Thus 
we are able on the one hand to subject the sea-bottom to a macroscopic and 
microscopic examination, and on the other to take out samples for further analysis 
of the surface or underlying layers, just as we may wish. The second apparatus, 
