14 
also constructed by Petersen, consists of a thick-walled glass-tube with a 
lumen of ca. 1 cm., a thickness of 1—2 mm. and a length of 50—55 cm. The 
upper end of the glass-tube is attached to a lead. When it is sunk down the 
glass-tube penetrates some way into the bottom and takes up a cylindrical plug 
of the bottom-material. Such a bottom-sample gives especially an excellent pic- 
ture of the arrangement of layers in the sea-bottom. If we wish to examine the 
single layers more closely, possibly under the microscope, the end of the cork is 
cut away below and the remainder is pushed up the tube with the bottom-sample, 
and the latter as it comes out of the tube can be examined for every depth. 
These glass-tubes are naturally only suitable for soft bottom; hard ground they 
cannot penetrate. On muddy bottom the adhesion of the bottom-sample to the 
sides of the glass is sometimes so small, that the sample slides out when the 
glass tube is being hauled up through the water. In such cases frequently the end 
is achieved by using narrower tubes. In too deep water, probably, it will not be 
possible to use these tubes. 
4. "Sea-bottom in Thisted Bredning. In describing the sea-bottom in the 
Limfjord we may begin with that in Thisted Bredning, which in many ways 
may be taken as to a great extent typical of the great part of the Limfjord. 4 
bottom-sampie from the deep part of the Bredning, taken with the above-mentioned 
glass-tubes, will show us the following: uppermost we have a very characteristic 
layer of 1—2 mm. in thickness. From its colour we may call it the brown 
layer. It consists of fine particles, which lie very loosely together, so that the 
surface has a fluffy appearance. 'Seen under the microscope this uppermost layer 
is found to consist of numerous particles, for the most part indeterminable as to 
origin. In addition to inorganic materials, particles of clay and the like, we find 
all sorts of other things, e. g. chitin needles, a few shells of diatoms and fairly 
frequently larger things, which are distinctly seen to consist of the tissues of 
higher plants. 
In order to determine the nature of the organic components occurring in 
the sea-bottom, I made some micro chemical analyses on a dried sample of the 
uppermost layer in Thisted Bredning. One might be inclined to expect some 
quantity of cellulose, but this was not the case. Only very few of the particles 
of the bottom were coloured blue with chlor-zine-iodine; the greater .part 
remained either colourless or assumed a brownish colour. On the other hand, 
Ruthenium-red, which as known gives a reaction with pectoses, coloured many of 
the particles intensely red. 
In the brown layer here and there we find some small, spindle-shaped, 
brown balls, which fairly easily suffer compression under the cover-glass, and 
which are undoubtedly excrements, probably of Lamellibranchs. 
Of living organisms, apart from bacteria and higher animals, there are but 
few; one or two living bottom diatoms are met with. 
Under the brown layer we find a layer of dark-blue colour, extending to 
the bottom of the sample and consisting of sand-mixed clay with organic remains. 
The whole of the bottom-sample is free of smell. ; 
A bottom of this kind covers the whole of Thisted Bredning outside the 
6 meter line. Inside the 6 meter line we have the Zostera belt and inside this 
