15 
again a belt of sand. In Thisted Bredning both of these belts are as a rule 
very narrow. 
The question is now, what we should call a bottom deposit of this kind. 
As mentioned above, the name gytje is used to indicate certain freshwater deposits, 
which are rich in organic material and which have arisen by the excremental 
agency of the bottom-fauna. It does not seem to me that this name can be used 
for a bottom-deposit of the above described nature. In this the quantity of 
excrement plays far too small a role. The main quantity of the organic material 
found in the brown layer has scarcely passed throgh any digestive tract and will 
scarcely do so. Mixed with inorganic materials, sand and clay, it will gradually 
sink down into the underlying, black-blue layer, without ever being excrement. 
On the whole it does not seem to me possible to find a common name 
for such a heterogeneous mixture as is found in the bottom-soil of Thisted Bred- 
ning. There is also the difficulty that a bottom-deposit of this kind passes over 
in other parts of the Limfjord without boundary into bottom-deposits of a similar 
character, but of somewhat different composition. It is common to probably all 
the bottom soils in the Limfjord, that they consist of an intimate mixture of sand, 
clay and organic materials, but these components are present in extremely differ- 
ent quantities. If the quantity of the organic material grows greatly, as is the 
case in many of the inner reaches, Louns Bredning, Skivefjord ete., we obtain 
bottom-deposits which resemble those we commonly cali mire or mud, and as the 
quantity of organic material and clay decreases, we obtain almost pure, sandy 
deposits, e. g. at several places in Nissum Bredning. I am thus inclined to think, 
that the bottom-deposits in the Limfjord should not be characterized by names 
but by analyses. And the characteristics, which should be of the greatest impor- 
tance here, are the quantity of organic material, clay and sand and carbonate of 
lime. In the following section a series of bottom-samples from different Danish 
waters will be discussed. At present I have only made determinations of the 
organic material they contain. 
5. Investigation of bottom-samples from Danish waters. The bottom- 
samples used in these investigations were taken with the 0.1 m> bottom-sampler. 
When the bottom-sampler was opened and the bottom-sample lay in its natural 
position on the deck, the sample for analysis was selected with a small spatula 
at right angles to the surface of the sample and to a depth of ca. 3 cm. Alto- 
gether ca. 100 gm. were taken, brought into a glass and covered with alcohol, 
the whole being then well shaken. On returning to Ccpenhagen the bottom- 
samples were dried at 607—70%, then pulverised in a mortar and again dried 
at 1009. 
In the material thus obtained the quantity of carbon was determined 
according to the method given by Kjéldahl (Medd. f. Carlsb. Laborat. III p. 110, 
1891). The principle of the method is to convert the carbon to carbon dioxde 
by means of concentrated sulphuric acid and bichromate of potassium, and then 
absorb and weigh the carbon dioxide formed. The splitting up was made in a 
long-necked retort with a volume of 100 cmZ. The retort was provided with an 
india-rubber cork with double bore for the inlet and outlet tubes, of which the 
inlet tube went right to the bottom of the retort. By means of an air-pump a 
